ZestyYou'd also have to be careful about conserving volume between the cylinder and the cuboid because it has a pretty significant effect on whether your directs/pipes hit or not.
More the volume, i'd say the projections (and on 2 dimensions out of 3 that's easy with a cyilindrical hitbox). But either way if a change like this happened i'd be more then glad to sacrifice bit of my muscle memory in exchange.
Speaking of making this a doable, i'm not so negative. It's not an hard work on Valve's behalf and i guess that if we persevere on demanding a fix like we did for demo det bug, then eventually they'll work on it
EDIT: are we sure that what allows to wallbug is the vertex of the parallelogram and not the corner too? Otherwise having a cylinder wouldn't fix it either (there is still a corner between the base and the height). Pills hitbox would be the only choice, but i'm afraid that would break many good things in jumps such as edge bugs, bounce, slides (?),..
This is one of the many times i wish Team Fortress 2 Beta was still used by valve for testing mechanics for future updates... Otherwise we can still test it on Team Fortress 2 Classc (the open source community project) and see how a change of the hitbox would affect the game