Doesn't work for esau and anyone else who isn't player 1

Well, it is possible, just I would need to make whole new mechanic for that (and I kinda suck a little in isaac api) so *maybe*
When I will be on balancing it, will consider it.

is it possible to make the brimstone bombs only do 8 ticks of damage, like normal brimstone, rather than the 13 ticks of brimstone bombs?

Perhaps a dark brimstone around the explosion?

Chill guys, there is other ways to balance it. I can either make it greatly reduce tear rate, make a switch in mod's config to allow you to change it's behaviour to like mom's knife + brim works now (which woul make dr. fetus shoot multiple bombs in the same time) or somehow add a charge bar to it. I don't think basing on a chance is good tho, it can be frustrating and not reliable, when other options could be better. Also brimstone bombs would lose their chance mechanic.

Those are bomb items. Bomb items are limited in chance, but the original item isn't. Hece Brim Bobs should be reliant on luck, Brimstone itself shouldn't.

Yes, special items are gone, but Brimstone is still a quality 4 (Meaning it still affects Sacred Orb, Tainted Lost and Tainted Cain), it costs 2 hearts unlike Brim Bombs, and it only appears in the Devil Room pool (Unlike Brim Bombs, which also appear in the Bomb Beggar pool).

The Brimstone ball would have to be massive for it to be worth. Rememmber, it must be a better synergy than 90% of all other bomb synergies, since Brimstone is quite rare due to pool exclusivity.

Some of the effects ARE chance based though...

For example, butt bombs, ghost bombs, sad bombs

Having it 100% chance for activate will make it too strong (considering special item system is gone, you will find brimstone and dr fetus more often).

I'd say make it chance based anyway but rework the effect to differentiate it from Brimstone Bombs.
What about a brimstone ball in the place of explosion, like that created from Forgotten + Brimstone synergy?

Don't make it chance based, the fact that Common Cold or others are chance based is based on how their normal tear effects are rare: For example CC has 25% chance to shoot poison tears, so it has 25% chance with Dr. Fetus to shoot Bob's Curse bombs; but Scorpio + Dr Fetus has 100% chance. Since Brimstone shoots 100% of the time, it shouldn't be chance based. Not only that, but that would also make it a copy of Dr. Fetus + Brimstone Bombs, when Brimstone Bombs is much less rare AND costs less than Brimstone. So it happening 100% of the time is fair considering the rarity of getting both items in a run.

Azazel + Dr. Fetus would be a small Brim laser. Tainted Azazel could either be a very weak, thin Brim laser, or a giant Hemoptysis area effect.

great mod! I had a slightly different idea - brimstone, which also has an explosion effect. I wish I could code ...

Blind - Will balance it further on updates, it is op now indeed.
Cadetpirx - To do, thanks for pointing it out, i forgor 💀

should be chance based, as all bomb synergies have now

Are you planning on Dr.Fetus synergies with Azazel & Tainted Azazel yet? Or does this mod already do that?

There could be some bugs with trollbomb sprites, so be aware of that until I fix it.