One thing I really don't like is option bloat.
I have a massive binder full of x-wing cards and it's honestly the biggest barrier to me actually playing x-wing.
It would be very easy to keep an army up to date and on the power curve by releasing new command packs and heroes. Suddenly all your favorite units have more options and choices that keep those models you painted relevant.
Also I don't think rune Wars benefits from massive numbers of unique unit choices. Each unit's dial is packed with very importaint information and having reference for enemy dials is a huge part of strategy and play. Therefor a few options is all you really need for an engageing game.
also more factions actually keeps more options relevant. If you look at FFG's lCG they have tons of factions for each game and do a pretty ok job of keeping them balanced and keeping core box set options relevant.