I have been thinking that the Animist and Druid are the one class and opening up the base lists to both. Do you think that taking that path will cause problems.
Are there other classes we could do the same for?
I wouldn't say it would cause
problems per se, but the concepts behind those two professions seem quite different to me, in that they share a set of concerns but differ greatly in their approach to those concerns. This is somewhat of a generalisation, but the Animist seems to have the gentler approach, of working with natural forces, empowering and enhancing them. The Druid seems quite a different beast, far more militant, drawing upon and dominating natural forces. In the campaign I used to run, certain peaceable or contemplative cultures couldn't become Druids (without the expenditure of a background option or two) but could be Animists and vice versa...
I also suspect the development costs - if you use the skills in RMC2 - differ somewhat. if you use the Druid as written in RMC1, then no problem.
Of course, by merging the base lists into one pool you create the opportunity for greater variation, and in that sense I think it's a great idea. If I did that and wanted to retain elements of the passive culture=Animist/militant culture=Druid dichotomy I mentioned above, I'd have to bar certain lists from that pool for certain cultures (no
Druidstaff for the contemplatives, for example).
In terms of other professions where you could pool base lists, you run into issues about realm variability and hybridisation. Are you wanting to do this to cut down on the number of professions? In a sense, this is what RMSS/RMFRP does (perhaps at the expense of recreating the problem through multiplying training packages).
You could try to merge the fighting semi-spell users (Noble Warrior/Arms Master/Warrior Mage/Beastmaster etc.) and the sneaky ones (Nightblade/Montebanc/Sleuth etc.) I suppose, but there are differences across realms that create problems, unless you go with full realm variability. In my view, you'd lose the nuances - and the crazy organicism - that make RM2 so rich and a worldbuilder's delight.