Broadly, yes. Although there are a lot of failure points.OgreBattle wrote:So making open multiclassing/feat grab bag work... knowing the failure points is key so how to avoid them?
Let's consider two abilities: the treadmill ability and the static ability. This could be anything from attack versus armor class to sense motive versus bluff for the treadmill abilities and anything from levitation to speaking Portuguese for the static ability. But for ease of conceptualization, let's make them directly opposed: Firebolts versus Fire Immunity.
So you can get an unlimited number of progressively larger firebolts to throw at higher level opposition, but to a first approximation fire immunity doesn't actually change or improve, nor does it need to. Both Fire Immunity and some example of a Fire Bolt would be appropriate to give to a 'first level' character, and the character with the Fire Bolt attack could receive a bonus to that attack at 2nd level and every other level forever. But of course, the Fire Immune character has the advantage over the Firebolt character at 1st level and they have the advantage at 6th level and the have the advantage at 31st level. All without ever getting a single bonus to their fire immunity.
Now if you want to, you can incrementalize anything at all. That fire immunity could be put on a treadmill of fire resistance where sufficiently higher level fire would blast through it. But of course that's stupid, and also 'You're still fire immune, but that immunity now extends to the monsters you would be fighting now but wouldn't have been fighting before' sure doesn't feel like a real ability.
What you want in character advancement is for everyone to get a mixture of abilities that progress as they go up in level and abilities that don't need to. And once you've wrapped your mind around that, and the fact that a treadmill ability that stops keeping up with the treadmill is effectively an ability you lose, you have a handle on what leeway you actually have with regards to your level advancement and 'multiclassing' options.
-Username17