I was emailing my group with this discussion just this morning. Here's a C&P from my email.
I've been pondering monsters in 4e lately. Here's what I'd like to see...
The old types (humanoid, monstrous humanoid, animal, undead, vermin, etc) become descriptors. These descriptors would help determine how the creature would interact with spells and such (i.e. creatures with the Undead descriptor could be turned by clerics)
BaB, hit points and so on are based off of role, with each role represented by a non-heroic class. Boss fights and superbad creatures should take standard heroic classes.
For example, let's say the Bruiser roll gives +1 progression to BaB, +2 to Fortitude Defense and +1 to Reflex Defense and d10 hit points (which, due to the fact that it's not a heroic class, is not tripled at first level).
Let's say the Striker roll gives +1/2 progression to BaB, +1 to Reflex saves, +2 to Will saves, spells and d4 hit points.
Thus, a 4th level Goblin Bruiser would have a +4 BaB and an average of 25 hit points and 2 feats, whereas a 4th level Goblin Striker would have a +2 BaB and an average of 10 hit points, 2 feats and spells/spell-like abilities to bring into the fight. Either of them would, theoretically, be a decent challenge for a 1st level PC.
This could lead to all kinds of fun with striker zombies, bruiser kobolds and sneak golems.
However, a 4th-level dragon fighter would have +4 BaB, an average of 45 hit points*, 2 feats plus a 4th-level fighter's bonus feats and talent choices. Additionally, they'd have draconic stuff (maybe extra hit points, fire breath and so on) as described in the creature's stats (but not **necessarily** tied to the [dragon] descriptor) and would be a challenge for a 4th level character (or four 1st level PCs). *Barring con modifiers.
This could make templates pie-easy to throw on. Undead dragon? Gains the [Undead] descriptor (possibly supplanting the main descriptor type) and the special abilities for the type of undead it's becoming (a dragon with the zombie template, for example, might gain the Slow ability (meaning it can move OR attack each round, not the ability to slow others) and would lose the [Dragon] descriptor and supernatural or spell-like abilities; hit points (but would lose the HP from Con since undead wouldn't have a Con score), BaB and so on could stay the same). Man, that'd make templates way easier.