Looking for Opinions

[Yogibear41]

Thinking of adding this homebrew rule to an upcoming game I am working on.

Characters and monsters gain an unnamed bonus to their AC equal to one half their bab bonus gained from class levels.

So a 20th level fighter would get a +10, but a 20 hd magical beast would gain no bonus.

What do you guys think? I expect the WBL to be a bit on the short side for the mid levels, thinking this might help even it out.

[WeaselGuy]

Seems to me like you're trying to give mundane nice things, which goes against the core rule of "mundane can't have nice things"

Seriously though, that's not a completely horrible thing to implement, if the intent is to boost the defenses of your adventuring party, and certainly not the most ridiculous thing I've ever seen.

[Yogibear41]

I have always hated the idea that a 20th level fighter wearing non-magical armor is easier to hit than a 1st level fighter wearing +1 plate, that is the main reason I want to do something like this.

[The Insanity]

If the 20th level Fighter wants to be better that dodging hits, he can take (Improved) Combat Expertise, he'll have enough feats for it after all.
There's also Defense Bonus (http://www.d20srd.org/srd/variant/adventuring/defenseBonus.htm) variant rule, which I find works good, especially with Armor as DR variant rule.

[(Un)Inspired]

It's gonna be a further boost to clerics.

[ace rooster]

There are a couple of threads where this sort of thing is mentioned, and nothing crippling has been mentioned. I would use it as a dodge bonus, but I don't think it makes a huge amount of difference.

One issue I can see is that it only delays the inevitable. An increase of CR by 1 equates to an increase of about +3 to attack for monsterous humanoids or magical beasts. A +1/2 increase to AC per level helps but is still dwarfed by this to the point where AC does not work against CR appropriate encounters past about level 14 (as opposed to 12).

If the only intention is to offset reduced wealth then it might work well, but it could benefit NPCs more than PCs, and actually penalise martials over casters.

NPCs have less wealth to start with, and generally do rely on AC as a defense. An ogre warrior 4 is CR 5, and in banded mail is rocking an AC of 21 as opposed to 19. At that point they are getting into the levels where a tower shield could be considered, bringing their AC to 25. This is not massive, but against PCs with an attack of +14 that +2 to AC will reduce damage by 20%. Given that the ogre will be attacking at about +11 PCs will need a starting AC of about 21 to be better off (at level 5). While this is possible it is not easy to get these numbers at level 5.

Casters will be better off because they generally do not attack AC, and actually find it easier to push their AC up anyway. Clerics and druids in particular get most of the benefit a full BAB character would get, but because extra AC is more valuable if you already have a high AC benefit far more. (If the enemy needs an 11 to hit you a +2 to AC will reduce damage by 20%. If they need a 17 to hit you then a +1 reduces damage by 25%.).

Hope that helps.