So light? That one admiral guy might have a chance then.
BB is a cheat, so first you have to have a crew to keep all of his crew occupied to even get a chance for 1-on-1. Then you have to not even bother with using a Logia ability to be etherial and then go full frontal assault. That would be fine until he added earthquake, so now not only do you have to have defensive haki stronger than his ability, but you have to have it active and attack. So you need a body that doesn't need a defense, that only leaves Paramecia users that have their constitution a flexible material. Paramecias are weaker, but more durable as regardless of contact with Sea Stone, their form is permanetnly changed. Luffy is the only Conquer's Haki user with a permanent passive defensive buff from his Paramecia. Rubber under extreme dryness or cold does not crack, so he just has to be able to hit his hardest while at his weakest to win.
BB can be defeated.
an All Out Luffy Rage mode, killer eye looks, max haki mode (armament,conqueror,observation), combination of gears mode (second,third and maybe a fourth one), the usual gattling gun not stopping (till BB is dead or to a lesser extent beaten to a pulp) and ofc luffy shouting RAAAAAAAAAAAWWWRRR!!!!! mode attack with bruises and blood and torn dress looks. so badass.
Seems like it also works in a similar way in OP world - when Aokiji froze Luffy, the crew needed to thaw him out carefully, and it's apparently so that even his rubber body wouldn't break.
^ What a nice reply! If there is no air for BB to breath then he's done for good.
Foxy's slow beam is useful, after hitting BB with it then dump him in the sea.
Best strategy for beating BB:
1. Be named Luffy.
2. Eat meat.
3. Get nearly killed by BB.
4. Complain you lost because you didn't eat enough meat.
5. Eat meat.
6. Spend 20-30 chapters trading blows with BB while your nakama finish off BB's crew.
7. Have a quick flashback to something that happened off panel earlier in the storyline (probably depicting consumption of meat).
8. Win by the narrowest of margins.
9. Eat meat because it's not a victory until you party!