my 2nd game plan is something similar (and maybe it will have 1st priority if test pre-works go fast enough):
a 3rd person game with a few selectable characters (knight, wizard, elf...the usual boring stuff I can get freely), using WJBender's navmesh pathfinder for enemies what I have tested in these days and seems to work fine. probably I have to integrate the navmesh plugin to my editor and add a player editor too (I mean a simple AI behaviour editor). only some avoidance should be added to AI movements, which can make development a bit longer. not a big scale game, just a few levels, and open source. sounds like fun?