This is the first I'm learning of gemrb. Thanks, it looks intriguing and promising. I only was able to give it a cursory look last night, and the website's down right now, but I'll check it out more later.
I downloaded and installed Faiths & Powers, and I like it! I was disappointed that there was no Dawnknight of Lathander for my Paladin, but maybe I'll use this opportunity to learn to properly build a kit for myself. It looks like the mechanic is an in-game implementation of what I'd been doing with my clerics through Keeper--assigning a very high number of memorizable spells, then filling them with equal numbers of all spells known, to emulate spontaneous casting. Very well done (and much more fun than stopping to use Keeper every time I level up).
I am a little confused about spheres and spells known, and couldn't find any documentation except the spreadsheet you linked in the main forum topic. I'm currently playing with Branwen (with a different portrait--ugh!), and naturally assigned her the Tempus kit. But she only has like 3 or 4 1st-level spells. So I checked the spreadsheet, and it looks like most spheres are allowed to her kit, although I admit I haven't yet gone through and carefully checked each one to see why it isn't there. My question is: are more spells gainable or somehow learnable, or do the priests of some orders just not have many spells? Or is it maybe a conflict with another mod I've got installed?
Lastly, since you like Clerics so much, I thought I'd share with you a tiny little thing that I made. I got tired a long time ago of Clerics only having one option for ranged weapons, and that not really a very good one, and so I made stonebows. This is only a very basic selection so far: light and heavy mundane, and light and heavy +1, with basic, +1, and +2 bullets, and an infinite quiver of plain bullets (because the way ammo is done in-game is tedious and implausible--arrows and bolts and slingstones are not expended on use like firearm ammunition! They're recovered after each fight, and broken or lost ones replaced in-between battles.) Anyway, thought you might like it, and it would be easy enough to expand upon with better bows and bullets, etc. I'm going to create a special undead-hunter stonebow next, and some holy bullets, maybe using the sunstone ones from the Amaunator temple. The trick is that you have to lie to IE (in some places) and tell it that the bullet is a bolt. The stonebow bullets and sling bullets are not interchangeable, which is accurate to life, because real slingstones are actually not round but lozenge-shaped. I'm actually thinking I'm going to change the names and descriptions of sling bullets in my game to reflect this and make them more easily distinguishable from stonebow bullets.
SBOW03.ITM SBOW04.ITM XBUL01.ITM XBUL02.ITM XBUL03.ITM SBOW01.ITM SBOW02.ITM QUIVER07.ITM