Possible? Sure. Unsafe? Definitley. A major part of the blades stiffness comes from the covering squeezing it all together. The best way to see this for yourself is to take a brand new set of wood blades and twist them. They will twist very easily as the plastic wrinkles. Then take the heat-gun to them and twist them again. You'll notice the blades are now a great deal stronger. Paint can't/wont do that.
If it could, we would be buying painted, non-covered, wooden blades, not making them.
There are many different blade manufacturers out there with just as many designs. If you can't find one you like, buy a set of fiberglass blades and paint those.
Airborne Models has some super cheap glass blades that I must say, are the best damn glass blades I have ever spun! And believe me when I tell you, I buy LOTS of blades (not necessarily a good thing!). A set of 600's will set you back all of $33.00! Paint those to your hearts content! http://www.airborne-models.com/
Once you fly a set of those, you'll nail those wood ones to the wall. Good blades do make that big of a difference. They make everything easier. You fly more smoothly, you can auto with confidence, the heli will be more responsive, etc. etc. etc.
The FRP's are the blades I "try" with to keep my PRO 600 Carbon's in one piece. You can buy three pairs of FRP glass blades for one set of PRO Carbons.
FWIW, every set of FRP's I have purchased have been balanced dead-on except once and they were oh so close (the difference between a set made Monday morning and a set made Friday afternoon
). You will need to balance again after painting but you will be that much closer.
[b]Murphy's Constant:[/b] Matter will be damaged in direct proportion to its value.