To be honest I would go as far as saying that not only it can't be stronger than what it was but also it can't be as strong as it was. Even if the bankai is different does an scenario where the bankai is as strong as it was is plain weird. The bankai damage is supposed to be permanent, are we supposed to believe that after being repaired it can get back to being what it was even in spite of what mayuri said? Taking what was said in consideration it would be absurd that a bankai gets new abilities out of the deal for that matter. I mean, the bankai is supposed to be permanently damaged and even the amazing reijutsu which the royals are supposed to have can only make it similar to what it was however fixing it results in a new techique? Honestly, even if the repair does result in ichigo getting new techniques out of the deal I don't think they would in fact live up to what should be expected of a full fledged bankai.
Now, if ichigo's bankai is weakened I do wonder if he would be getting weakened versions of the techniques he had. That would be a particular issue with getsuga tensho but what about if ichigo gets a weakened version of saigo no getsuga tensho? The normal FGT resulted in ichigo losing his powers however if he gets a weakened version of it I could see an scenario where ichigo can use it as much as he wants. It would obviously not have as much power as it would in a normal scenario but if ichigo gets a version of the technique which he could use consistently through battle it could be said to represent an actual increase to his average fighting strength.