I suppose it's a matter of whether you want to make it secure or if you just want it harder for a specific individual to pick. If it's security than variety is the key (pun intended). Perhaps using a longer pin for one of the top pins just so that when bumped, the shear lines don't clear in unison. The LAB re-key kits have spool pins suitable for bottom pins, if you use one of these as a top pin then a lockpicker expecting a spool pin would pick up on the false set, back off the tension a little and nudge the pin up but instead of finding the bottom of the pin would just find more pin and may second guess himself. As to the tolerances between the plug and the housing, perhaps you can find some brass foil to wrap around the plug till the fit is tight and then braze the plug or perhaps wrapping it with plumbers teflon tape would make it a tight fit. Kwikset recommends that the anti-pick spool pins be in the front three pins closest to the bow with standard top pins in the back two because the key enters from the front so the standard pins would hold the plug with less give for longer but this only help defeat lock pickers who pick front to back, you don't have many options with just five pins so it is a matter of which pins you think will be picked last, the less give means the less feedback on a set.
To a certain extent, beefing up a Kwikset is a matter of having a wolf in sheep's clothing, to lure an overconfident burglar into wasting more time and hence increasing the likelihood of having the suspicious activity spotted. Imagine if you will having an enclosed porch arrangement with the outer door being a beefed up Kwikset and the inner door being a Medco, that would certainly give the would be thief the message that he best go elsewhere's.
I think there's some value to beefing up a Kwikset as it presents an unexpected element to the burglar and most theft are crimes of opportunity. Any lock can be bypassed if targeted.