"Is there such thing as self induced leaf necrosis in cannabis?

Well, it's more often grower induced.

Can a mature plant produce necrosis-ed leaves due to root bound? Say a 10 week veggied plants in 5gl buckets.

That's just one of the symptoms of a rootbound plant.
After 10 weeks the chemistry becomes almost un-controllable.
The soil salts up and all attempts to balance PH only exacerbate the condition.

If you have the headroom, you might try stacking.
Prepare a bucket of fresh, moist, medium.
Drill honkin' big holes in the bottom of the existing buckets, and stack them.
The existing damage will not repair, of course, but the new growth should pretty up.

Also what would be the ideal canopy area/foot print for these plants."

Not sure I can help you there.
Generally, I play it by ear.
The question has many variables and I don't know from ideal.
I jus' know from "good enough".
An' sometimes, half-assed" is more than good enough.

I'm sure there's someone here that can give you a mo' betta answer.
Try re-phrasing the question.

Aloha,
Weeze.