Here's the issue that I ran into: I wanted to use RfTools as a late-game, safe dimension maker based on power, and mystcraft as an early-game, lots of instability dimension maker based on greedy ages.
The problems? Well, even if the only source of RF is rotarycraft, and even if I can tune RfTools to require more RF/t to run a dimension, the truth is that you can hook up 4 steam engines to a rotational dynamo, and get about 126 rf/t; if you need more, you can hook another 4, and then combine the rotational dynamos. Heck, you can do that for as many steam engines as you need. The result is that an RfDim is never needs more than a steam engine, so there's never any need to worry about gear boxes, lubrication, automated gasoline production, etc -- just a DC engine to pipe water out of the ocean.
(And then, I just found out that age creation, even though it might say that it takes N RF/t, really just means that it adds up the RF until it gets N, and then does one tick of work. )
So no matter what kind of dimension you make, it's not a late-game thing; it's as early as spamming steam engines and pipes (steel/redstone/glass/etc.)
Honestly, my biggest issue would just be the gunpowder for the steel making.
In a finite water world? If the water flows, just start your pipe down at the bottom. If the water doesn't flow? Then your pumps will pump a hole in the ocean at some point, and you'll move them.
(Hmm ... can a steam engine run a dew point accumulator?)
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In general, you cannot run a RoC device until you have the powergen infrastructure for it. But you can run an RF device off of anything, as they have the model of "accumulate power until there's enough for a tick of work". And even if you can modify their internal buffer behavior to say "we'll empty the buffer after every tick, so either you had enough to do something this tick or you did not", you can combine arbitrary many weak power sources together; there is no concept of "This machine is harder to run than that machine". Only more expensive in building more generators.