Well good thing we all got around to answering this question 4 years later
My opinion the bubbles wont get larger on their own. Flexing the plastic may make it get slightly bigger.
Exposing the air in the bubble to heat causing the air pocket to expand may also make it larger. Just all depends on the amount of heat and how well the nonbubbly area near the bubble is adhered.
This the guy you were thinking of Michael Koytluk (worlds only lenticular restorer) <--- taken from LAMP (never seen a before or after example)
And to repair a crack I am guessing would always be noticable but could be stabilized.
If I had a large bubble would probably try to make a super tiny hole with a needle to release the air before lightboxing it. but only if I noticed the bubble swells in heat. In addition some type of adhesive could be injected and air could be pushed out from the bubble so the backing stays affixed.
I don't recommend trying anything without testing on a lesser lenticular of course.