[thejeff]

If I'm right about what you're talking about, the pool is liquid. To test, start with an awake rainbow and split his research between 2 paths.

As the numbers get bigger, the interface makes it hard to split it exactly where you want, but with a few hundred rp being off by a couple is usually not an issue.

I would like the lock out feature, though it's rare I want to work on three paths.

What I think I'd really like, inspired by your post, would be an entirely different system for assigning research. An interface that would let you specify what levels of which paths you'd like to research in order. Rather than "18 more points to get to Constr 4, then the rest into Conj. Next turn I'll finish Conj 3, then work on Evocation", you'd say, "Research to Constr 4, then Conj 3, then Evoc 4" and your research would be allocated as needed.
This would also eliminate my most frustrating thing with research: Carefully adjust research levels to finish the current target and start the next, then remember I wanted to forge or cast something. Next turn, 4 points from finishing the level.