I have a big problem with this tweak. I started game with barbarian but I do not get 12 HP/level but only 10 as a normal fighter. I started to find cause and this component is guilty.

Barbarian HPs are linked with hpwar.2da very disastrous way. I think (according to my research) that game (exe) will add 2 points to sides in hpwar.2da. So because this tweak remove rolls these additive HPs does not applies.
And another misery is that when rolls are higher than zero modifier column is ignored.

If you do not understand me well I created a table:

Ok, I found nothing important but I was able to bypass it via class abbility. You can look at http://addoncz.jinak.cz/viewtopic.php?t=247.

That's interesting, Drake127...Good job on that max HP at levelup for Barbarians. If now you could just find a way to make number 12 displayed at levelup...

Well, I really tried to create some brilliant solution but without success. I wonder nobody notices this bug before because everyone with this component (no matter who made it) is affected.
My solution is unwieldy but it has one huge advantage - it is only working. I'd like if you help me to make it better.

Troubles with hpwar.2da I already noticed - please take a look at fourth and fifth row (including heading) in table above. It is strange behaviour (How you can roll 1d0? Why bonus is ignored?) and I can only guss how it is really interpreted.

When we give up to solve it only with hpwar.2da we can use class abilities because on every level Barbarian missing his two HPs. I did spell that adds these 2 HPs. But these two HPs will not show in Level Up dialog (Additional Hit Points Gained).
Second cosmetic problem is related to Timing Mode. If I set it to 1 (write directly to cre file) it works only when player levels up. If this spell is applied when creating character (1-7 level) it does not work properly and double these HPs (it adds four instead of two) - I do not know why.
So I set Timing Mode to 9 (add permanent effect to the cre). I am not satisfied with this because it makes character file "ugly" by presence of Max HP Modifier effect nine times.

footnote: when we are talking about acurrate HPs be aware that BGII adds one level more HPs than character really should get.

Well, I found that Timing Mode 9 is not as stable as I supposed because I lost these additive HPs twice (and I have no idea why (between few minutes on graveyard).
So I tried to figure out with Timing Mode 1. After years of hard work (ok, few hours) I found that spell is called twice (during creating character). Don't ask me why - I have no idea. But solution was not so hard. I used Protection from spell and (thanks to igi) Timing Mode 8 (permanent until reload) because we do not need to store this effect to cre.
I am much more content with this and the last thing remaining is to show these HPs in Level Up screen but I start to think it is impossible.

I added to this version Starting HP Fix because BGII double first level roll.

http://addoncz.jinak.cz/viewtopic.php?t=247

Nice to see your Mod improving, drake127. Unfortunately I am no modder myself so I can't be of any help although I wish I could!

I have one (maybe) stupid question. Can't we create a specific .2da HP table just for Barbarians ? I mean...The problem seems to be that Barbarians are considered by the game as a Fighter kit and this limits the HP roll to 1d10.

Do you think there would be a way to change this situation ? Thanks!

Unfortunately not. Use and names of 2da files are specified directly in bgmain.exe. So without source code there is no chance to change anything. With GemRB it would not be problem to create such table but it is future for meantime.