Knowing is half the battle
Shafts will warp until the residual stresses are equalized. Shafts can be straightened because wood is subject to plastic deformation.
Your shaft warping will not ever affect your play unless you let it.
100% Truth....very few players even good players have cues that are DEAD STRAIGHT....some get close but most cues are crooked plain and simple.
You can actually "Plasticize" wood using anhydrous ammonia (i think thats the chemical) in a pressurized chamber for "X" amount of time....I always wanted to do that to a solid maple plain jane and bend the cue in a semi circle or something....and its supposed to hold shape and bend way better than steaming could ever do.
It sounds very elaborate but i would love to build a rig to straighten cues and shafts with it......not sure of the effects on the glues and such, there is no water involved and the ammonia escapes the wood within hours as opposed to possibly months with moisture.
Some rifle smiths do the types of wood bending your looking for tho and heres a few of the techniques they employ:
It depends on the stock finish as some guns have hard oils....
If its oil finished wood you can hold it in a vice using cloth to protect it.
Place a bath of linseed oil under the bit to be bent and place a tea candle or some other heat source under the oil container and when hot pour hot oil over the bit to be bent.bend it gently to over what you need and fix it untill cooled.
Example 2:
Its exactly the same as #1 but use a hot air gun to get the wood hot. this softens the resin wood fibers. Bend it gently when hot to 25% more than you need and keep it there till cool.
Example 3: (
for cues imop this is the worst option)
Its the same theory tho instead of using oil, put a bath of water under the wood to be bent. With a burner under it cover with a heavy cloth and let the steam heat up the stock. Over bend as in above.
All the above work. But remember after you release the cold wood it will relax about 25%.
The only problems with these methods is you would most definately have to build some sort of jig that would have some sort of moveable pegs to adjust for the taper....
WARNING: Don't try this on your cue....if you want to play find some junk wood or junk cues to try it on a handful of times before you even think of trying to do any of the above to any descent or good cue....if you screw something up its on you my friends.