If you take your time, I'm sure you could do a fine job painting the baffles. The key would be carefully taping and papering off the drivers and grill peg holes. If you prepare everything properly you should be fine and also you'll be able to paint them the exact colour you like.
The trouble with the grill painting being "unproven" is mainly due to the fact that these in-cabinets are relatively new, as well as the fact that, imo, the majority of people are still buying the regular speakers vs the in-cab's so there's not too many out there who've done this so far. Axiom could provide the details on painting the grills, I'm sure.
You're idea about having Axiom wrap the baffle is good too! see what they say.
