I think, based on very little (well, I suppose the aforementioned Karaka 'kill' of an elder) that there will be more variation in power levels of the FUG elders than your 'run of the mill' CC, which seem to be probably close to on par with each other. Excluding Adori ofc, who it is my personal head-canon until proven otherwise she is also operating as the 1st CC. While I also wonder how many CCs there actually are (at least 2 more - possibly 3, but maybe multiples more if there are <5 corps...), but I digress.
Older is generally understood as stronger in the tower (as you get stronger with age AND have proven to have survived the dog-eat-dog enviroment that is essentially 'survival of the fittest' - as such only the strong should be left from ancient times), and FUG elders should be just about as old as anyone can be in the tower, so there's that. But, then there is the fact that not everyone ages into strength at the same rate, nor starts at the same point. Case in point Kal Rahim, 'Wall' chairman and clearly on the older side (presumably a ranker) yet unable to defend to the same extent as a Slayer or Wall Hero would be able to do (by virtue of being reliant on either and/or their respective armies). As such, not every ancient elder is automatically CC or CC+ level, though maybe likely. Soo-oh is another, just as old as Khel (or thereabouts) and yet she was roughly matched to YHS. While she is a guide rather than a fighter per se, it is just very clear that being old is not the be-all, end-all for strength, though those that survived that long probably trend on the stronger side.
The point is some FUG elders might 'just' be elders by virtue of being around from that time frame (maybe some were lucky to survive if not on the beastly level). If Khel was the strongest proto-FUG had at the time, he is the ceiling for the strength of an elder (excluding Luslec himself if he even counts). Unless for some reason a freakshow aged into strength at a stronger rate than even Khel (is it linear... or?), he's the top and the ceiling. Sophia is likely close, but not quite Khel level (as much fun as it is to shit on Khel). There's also the ancient beast in Khel, which is very rare. Sophia with an ancient power perhaps.... though Khel in the flashbacks did not seem to have/use/rely/have even met the ancient power he had at the time he was proto-FUGs then champion. So, he likely is leaps and bounds higher than the next tier of elders (even including Sophia) once the ancient power is considered. Sophia's showing was significant, but how to extrapolate that into raw battle power who knows. I'd say she is quite easily CC considering Frieza was the next-closest to Kalla and she would dwarf even Frieza's lighthouse abilities. Does that mean she would surpass a CC light-bearer (if one such existed)? Hard to say. Would be an interesting turn of events to find out Sophia has an ancient power as well (we really haven't seen the extent of her abilities), and the Luslec shoe-horned one into all of the foundational elders...
I doubt many small fry from that time period survived the battles, but not every elder automatically has to be tippy-top. There could have been some ancient divco (or even lower tier) FUG elder equivalent.
Take Khun Hynd Luch for example. He was around when Khel was, but clearly not as talented as Khel (then or present time). He maxed out at present-day divco levels. Had he stayed in FUG (or rather ancillary to them, likely later consolidated), he'd likely have been considered an elder (maybe) due to him coming from the time of their formation (essentially, elders are foundational FUG members). The same with the Wall Heroes - which have been highly debated as either being <CC or MAYBE on CC level, but slightly less. Cha is a wild card here because SIU won't let him comfortably show his abilities, but at least Dowon isn't screaming CC level. On par at *best* for her.
Taro York I'd venture to guess is present-day divco level as well (maybe even lower). Had he not been captured he might have made it to the elder table as FUG consolidated Genesis heroes, particularly Hidden Grove.
Toro is even more underwhelming, as ancient as he is. I can't imagine he would even be a tough fight for a divco in the Z army.
And while proto-FUG existed in some form before Hidden Grove, there was some overlap in the timeline. Khel was the best of early FUG, and took the best Hidden Grove members (all mentioned above) as the cream of the crop to work alongside a young FUG (Khel himself and some others) as an ill-fated strikeforce against Zahard. So they (Hidden Grove members) would qualify as what Khel considers strong anti-Zahard forces for that ancient period (during and after 'Genesis' however long that was) and come from the same ancient cohort as Khel himself, a defacto FUG elder and founding member as such. Khel had not necessarily preexisted some of the Hidden Grove members, though proto-FUG (those that fought with V and Arlen when they initially defected) did. FUG was technically established in the Age of Genesis when Hidden Grove also operated. I wonder if Khel fought under Luslect pre-Genesis as well... was it a 'requirement' to be an elder of FUG to have fought under V/Arlen/Luslec? Or just anyone that was strong and against Zahard at the time Luslec decided to continue carrying the flag? If the later then Hidden Grove members could have technically qualified - had they not all been killed, sealed, or taken prisoner. As such they are a good measure of what a FUG elder *could* be, coming from similar time in the Tower.
We don't know how many elders survived the foundation of FUG either. We basically only know of Luslec (he counts as one of everything in FUG, really), Khel, Soo-oh, and Sophia (3-4 tops... are there any more?). Hell, that might be it same as there might not be any more than 5 (or less) CCs. Alternatively, there could be more of either or both.
In any event, absent Luslec, I think Khel is an outlier.
This is contrasted to CCs which should be roughly equivalent in strength. Maybe. They are current corps leaders that have to be qualified in the power level associated with the position, so the creme rises to the top at roughly the same level, and in the same period (contemporary). Unless there is some thought-process to the corps number in relation to force projection (ascending or descending level of power), then CC2 should be roughly CC5 and so on (even as far as the total number of corps... CC33?). As expected from a military where ranks and structure is repeatable more or less. CC1 who knows because Adori, but it may also be that CC1 is another character roughly in the Kallavan-class tier. Much like Yas. That is to say - predictable and uniform.
So, if Khel is an outlier (although not everyone is even convinced Khel and EVK are CC+ level), and possibly (probably) surpasses a run-of-the-mill CC, what does that mean for all other weaker elders then?
THEN
What of the Slayers themselves? If the Slayers are positioned as, well, slayers (of FH's) then they would presumably have to be the top-tier of what FUG has to offer. Much has been said about how they have a fool's errand to do as they technically can't kill a FH anyways, regardless of strength, but also current Slayers quite simply are no match irrespective of the immortality contracts the FHs hold. OK, so there may have been stronger first-gen Slayers, right? They were ancient and thus had to be what you'd consider 'qualified'.... only Yama has been compared to them himself, by none other than Khel who should know their abilities.
So what then? Are Slayers just ceremonial and nonfunctional? Technically yes, but what if the immortality contract can be voided, destroyed, bypassed, or rescinded? Well, Slayers STILL ain't shit. Even the first-gen ones if you consider Yama is indicative of what they can muster.
The whole point here? Well, if we consider the assumption that all (or most) elders are CC+ level (the consensus here so far) while the slayers themselves are barely CC level (arguable, but certainly not CC+), then why the fuck aren't the elders the Slayers instead, while the Slayers (weaker) just operate as 'helpers' to the elders? Elder divcos essentially.
FUG composed of elders as the strongest FUG has to offer would then be functioning with a weaker set of Slayers which are absurdly supposed to be strong enough to kill a FH (one day...). Does not compute.
