It seems to me that TPs are completely different to the core RM assumption that professions are aptitude templates; they describe what you choose to learn and reflect the synergies in learning particular things together, but their base cost is fixed by the pre-existing aptitude templates. That doesn't mean there should be a profusion of professions or that there shouldn't -- there should be as many as we think there are aptitude templates -- but the difference between profession being what we can learn easily and our actual skillset being what we chose to learn puts TPs on the latter side.
I always felt that, for example, there needed to be a non-spell-using ranger-type (never liked the rangers-casts-spells archetype); TPs don't make that happen, they just make it easier for a non-spell-user to accumulate the skills, for every member of class X. For TPs to achieve the same result as professions would produce a large number of TPs; at best, I think they approximate it but I think it'd be easier to identify the core aptitude templates (and in my opinion, it's short of some core archetypes that were added later, like a non-spell-using outdoors type, and a barbarian, for example; I also like the burglar profession for a thief who just isn't suited to wearing armour).
From my point of view TPs might be more engaging as an approximation if they didn't get complicated and numerous themselves. I think that it's a difference between RM2 and RMSS/FRP (although they appeared in RMs in at least the Arms Companion, which is my least favourite RM2 companion of all although not just for that reason) and the people that play them, at least in some cases. TPs as substitutes for other non-core professions would almost be a deal-breaker for me, it just doesn't fit how I understand Rolemaster and it's underlying ethos. The idea of TPs -- that there are synergies when you learn skills together, making the aggregate gain in each bigger than if the same time was spent learning each separately -- seems sound to me, but it doesn't say anything about character aptitudes, which is what professions are. The aptitudes are only reflected in different total costs, but that's because the individual skills have different total costs for different aptitude templates; that's OK where we feel that the difference between archetype A and archetype B is just a matter of individual choice about what to do, or circumstances driving decisions, but if we think that barbarians aren't just fighters who don't like to wear armour, then different aptitude templates are required.
I agree with Grinnen Bearitt's point about core classes with a modification system being a Good Thing, I just wholly disagree with him that TPs are that system. The modification system should act on the skill costs, in my opinion, to produce what are, in effect, new professions from the core ones (but either ad hoc or constrained; no need to publish large lists of professions, then, if that bothers people or, even if they did, they'd be better-balanced).
