I think that RDM should get all the -II versions of spells they don't already have once either WHM or BLM gets a III version. (ie. Raise II when WHM get Raise III) I understand Raise III is expesive and ahrd to get now, but if WHM don't want competition for RDM I'm sure they'll go for it. Personally though, I don't see why we don't just keep WHM, because full access to all the -na spells, and the multiperson spells, not to mention divine seal to make things like Erasega.
as for job abilities, instead of getting one form another job, I think that RDM should get one that takes half of the idea of Divine seal, and half of Elemental Seal. (basically get a better chance of getting full power out of a spell, and even a 50% increase in overall effect). It wouldn't even bother me for it to be like a lv30 ability. But that's what I'd like to see for RDM.