Will a flywheel weight help slide the rear?

That seems like solid logic, though I have no practical experience to help you with.

I agree with carlsoti...it does sound logical but I havent tried it myself(I'm running a slipper clutch). Are you using a slipper clutch or just using the clutch lever? I know you said the bike is basically stock but just thought I'd ask. If your just trying to induce the rear coming around, try getting on the front brake a little harder and feeding the clutch out until the bike starts reving upand try to maintain a certain rpm a little shy of the midrange. Eventually you'll get results. Is it a race bike or street set-up?

Stock clutch, track only.

just for the sake of practice try dropping three gears and let the clutch out fairly quick. once the rear starts to chatter use the clutch to feather out the chatter...the wheel will still be rotating, but slower than the speed you're going, which is why the rear wants to come around. it's going to take some practice but you'll get the hang of it.

sure, it might break the tire loose easier but sliding the bike consistently is all about rear brake control...

I'm with WFO. Are you using rear brake at all? I down shift and feed the clutch in and out as needed to help control chatter and use the rear brake with some body english to step out the rear.