You could have 8 thrusters: two on each side, 4 rotating clockwise, 4 rotating counterclockwise. You could write a program on a ComputerCraft terminal that controls redstone signals to the thrusters of the correct direction and the correct number of them to be on which determines the speed.
This would be fairly easy. The output is variable for computers for the strength of the redstone signal. Create a line going straight out of the computer on one side. Program that to be 0-4 for spin left. Hook up repeaters down the side of the redstone line (an analog to digital bridge,) and connect the repeater output to the thrusters. Repeat for right.
For those without computers, or for testing, the gold weighted pressure plate could come into play. Or for an interesting twist the spin could increase by a daylight sensor.
We had planned at some stage to add a Galacticraft spin control panel which would wirelessly control them, but that would be a lot of work (would need a new block + GUI and a way of knowing which thruster is which, I am planning a kind of map as I don't want to have yet another block with frequencies). Redstone is more Minecraft and is something we can easily implement.
This is why I didn't approve of a GUI. More code than it's worth. Adding redstone means using a vanilla feature most mods also interface with. It also opens up a lot of possibilities, such as spinning only when my MFSU has energy. Things of that nature.
While we're at it, can I request redstone-controlled arc lamps? Perhaps a vote on whether it's switched off or on. I'd have to side on redstone turns it off, since otherwise it would
require redstone to work. Same with thruster. Default on, apply redstone turns off.