-Base power - LF can finally use his power to counter loops and gain a bit of distance not just punish bad positioning. There's still enough counterplay to this with windows and pallets etc for his base power which makes the better player come on top. Also the idea of proper timing for prolonging the duration of his power is great since it gives him more depth and creates space for mistakes.
Main thing that still could use more changes is the Tantrum. I think the idea of it is mostly fine but when I consider that quite a few of the new addons are based around improving the tantrum like giving it more speed or making it last slightly longer, I think it should probably be more then just a cooldown. So either rework the tantrum addons or make tantrum a real useful mechaic that is worth improving via addons.
For example make tantrum move at for example 60-80% base MM speed but add the empowered wiggling effects to it (from base wiggling + boil over) or some other hinderance that makes it difficult to follow survivor after getting into tantrum.
Overall the power rework made him justice and he doesn't really need almost any other changes.
-Addons - First of the new Iridescent addons right now are bugged so I'll just say that their bugged version is insanely OP thus I can't give any real feedback on them.
Very rare addons are all usefull and their effects are well designed.
Rare addons are more controversial. Shop lubricant, begrimed chanins are just base perks which isn't horrible but they're pretty uncreative, some small additional effects would be nice for them. Grisly chains and beast's marks addons are both decent. The grease either needs new effect since improving tantrum by miniscule effect is as useful as old chilli addons or significant change to tantrum making it into more then just CD mechanic.
Uncommon and common addons are fine except again those that improve the tantrum, those should get either new effect or have tantrum rewoked into usefull mechanic.
-Base power - First off, I don't think that the rework made Billy horrible killer, it just made his kit far less fun to use. If the current version goes live, billy won't be as played as he used to be not due to him beiing weak but rather due to him no longer beiing fun to play. It's just like when nurse rework came, most of her addons became pretty bad and her power was made more frustrating/unfun to use. Same thing is happening to Hillbilly which isn't fine in my book.
So I propose these changes to make his new cooldowns less punishing.
Actively revving should overheat at 5 charges per second, actively sprinting adding 2 charges per second is fine.
When not using the chainsaw, the heat meter dissipates at a rate of -10 charges per second
When the chainsaw overheats, the heat meter dissipates at a rate of -20 charges per second
-Addons - His new Iridescent addons seem quite underwhelming and could probably use some buffs.
Lopro chains are fun and gimmicky to use but don't really provide super usefull effect since in order for them to work, survivor has to prethrow the pallet and then run in a straight line otherwise you won't be able to land a hit on them due to poor base steering. Also permanetly disabling your instadown just for mediocre effect isn't wort it. Either add more positive effects to them or make it so that the insadown is only disabled if you break the pallet via chainsaw.
Iridescent brick is situational based on which map you've gotten. I don't really feel like it needs changes but that's probably because people will alway use it with map offering so if that's gameplay you wish it to have then it's fine as it is.
Now, I won't comment on all addons that have something to do with overheat mechanic number changes since overheat needs baseline changes so those will need new effects.
Very rare addons are decent except tuned carburetor. 4.4 m/s for moderately faster charge. I don't know how could you ever make a community meme into addon. 4.4 m/s killers have usefull chase power and billy's power addonless isn't the best anti-loop power even when at 4.6 m/s so please stop making addons like this unless you give them real compenastion for such insane loss of MM speed. If you want to make it not a meme then add to it massive decrease it terror radius (like 16m). That would at least make sence and create new billy playstyle insted of just creating crippling addon.
Rare addons are in my opinon the best designed addon you've made for him. They're thematic, usefull and even fun. Good job on those.
Common and uncommon addons are as usefull as common and uncommon addons tend to be.
Also to comment on perk changes, these are all great and I would love more changes like this more often. Even when reworking killers is nice and all perk changes mid-chapter patch is something I look forward to the most.