The only real design suggestion I would give is make sure the bottom is non-slip.
Usually you are resting your hand on the CP and pounding enough buttons to keep the CP relatively stable in most games.
The back-and-forth motion on Crazy Climber is a different story though.
It will tend to slide the entire CP on you, if you're not careful.
As far as which joysticks to use, I've had ALOT of experience in that arena lately.
I'd recommend Happ Competitions for a good all-around stick, based on the following experience, but would highly recommend that you get them from GroovyGameGear, with the aftermarket balltops on them.
I bought a dedicated Crazy Climber that had intermittent stick problems with the factory sticks.
I first built a quicky replacement CP for it, using T-stiks.
At first I really liked the short throw on them, and their overall responsiveness.
The stiffness of them got old really quickly though.
Next I tried my "favorite all-time sticks"--a pair of Wico leafswitch sticks.
I built a really nice custom CP to house them, got it all put together, and decided they didn't feel even CLOSE to right for the game.
They were way too mushy feeling.
Next I tried one each of the Happ Supers/Comps--which I normally don't care for.
Nice overall feel to them, but the bat handles feel absolutely wrong.
I solved this by hacking a set of Wico balltops onto them, and that improved the feel tremendously.
The Comp had a better feel overall, so I decided to go with them.
I tried the Comps, one each with the factory springs, and the heavy springs.
I decided that the factory springs felt closer to what I was looking for, so I decided to go with them.
The sticks still felt a little unresponsive in the up/down directions though, due to the microswitches not engaging as quickly as the T-stiks or leafswitches.
I've solved that by putting a set of T-stik switches on the up/down directions of each stick.
That makes them engage quicker in those two directions, without having any problems with going diagonal accidentally because the left/right still have the factory switches on them, and have to move farther to engage.
That lets climb quickly, but still lets you dodge quickly to the sides.
You just have to move farther to do it.
My only complaint at this point is that the 3.5" sticks I had on hand are a bit short, mounted under the wood CP like they are.
I plan to rectify that soon with a set of GroovyGameGear's aftermarket 4" balltops.
Once that's done, I should have MY perfect Crazy Climber sticks.
Your perfect sticks may be different, depending on feel/personal taste/playing style/etc... however.