A mod to implement both the current, oddly-powered pistons/droppers/etc, and a new version that lacks the odd powering system, so that we can demonstrate to mojang that the cleaner ones can do everything the old ones can do, and that there are some things that are easier to do with cleanly-powered stuff.
That reminds me of an idea I had a while back:
A new type of sticky piston that
(a) Emits a redstone signal from its head when both extended and powered (therefore acting like a three-block repeater, when paired with a block of cobblestone)
(b) Does not retract if it cannot pull the block in front of it back with it
(c) Briefly emits a redstone signal from its head shortly
after it retracts
but otherwise behaves the same way as a Vanilla sticky piston.
This way, if you make a line of several pistons and power the first one, the whole line will extend and retract. When you power the first piston, it will extend, push the whole line outward a block, and then power the second piston, which will extend and power the third, and so on until the whole line is powered and extended. When you remove the signal from the bottom piston, it will cease to power the second, but not retract because the second piston is a TileEntity that Vanilla pistons can't mess with. That will cause the second piston to cease powering the third, and so on until the last piston is unpowered. That piston will retract, then send a redstone pulse to the block it just retracted, which probably won't do anything. However, this will allow the second-to-last piston to retract, so it will do so, pull the last piston back, and give it a pulse, causing it to pick up the block it was pulled away from and give it another probably useless pulse. Now that the second-to-last piston has retracted, the third-to-last can and will pull it back and pulse it, causing it to pull the last piston again in the same way. This will repeat until the whole line has retracted again.