I'm looking at the prestige class Arcane Archer and one of the requirements is +6 BAB. My sorcerer won't have a natural BAB of +6 until level 12, which means that if he becomes an Arcane Archer, he'll never see the level 10 Arcane Archer ability "Arrow of Death"
Is there a way to raise BAB outside of leveling? If there is no RAW way, a balanced homebrew solution would be acceptable.
By RAW, only leveling.
Base Attack Bonus is a class feature, and it changes when you gain a level in some class.
Though there are prestige classes that advance spellcasting AND base attack bonus simultaneously, for example Eldritch Knight. Take a look around, there should be more of them, at least in 3.5 there were.
You also might want to adapt Battle Sorcerer class variant, which has a cleric BAB progression.
From the houseruling point of view, consider this: most classes and prestige classes are already kind of balanced in terms what abilities do they offer. Sure, there are less powerful and more powerful abilities, but generally speaking they are already fine, at least in BAB department. Surprisingly enough, prerequisites are also often well-written.
Now, we must also consider that the Arcane Archer was designed as a master of ranged combat (hence the high number of feats and BAB requirement), who dabbles in arcane archery. Sure, one might houserule the BAB requirements away, but that ceases to reflect the original design, so I would advise agains that.
To sum up, a balanced solution would be either
The traditional path to Arcane Archer involves multiclassing into Fighter or another combat-focused class that gets +1 BAB per level (instead of the Sorcerer's +1/2 BAB per level). Typically the Arcane Archer has a mix of an arcane class (wizard or sorcerer most often, but others work) and a martial class that can use bows well (fighter or ranger, but again, there are more options). Fighter 5 / Sorc 2 (or Fighter 6 / Sorc 1) can qualify for their first AA level at 8th.
From my own experience, yes, but it's problematic. Commit to an adventure path or other pre-written adventure with your group, and when one of your number leaves for the foreseeable future, convince your GM to allow gestalting so your smaller party will be up to the challenge. Or just beg to Gestalt period.
