Parallel class progression

[Lord Magus]

Our GM allows PCs to progress in a non-combat class as well as the usual character classes. Those classes are distinct from the NPC classes, have a maximum of 10 levels and use a separate XP tracker. Though they grant class skills and skill points at each level, they do not advance saves and BAB, and do not count toward total character level (so they don't advance base feat progression). So... I was wondering how to best approach the coding of those.

As they are significantly different from PC classes, not advancing BAB or saves of base feats, I thought about making each level a separate template. Is there any other approach that would be easier or more logical? Thanks!