RV 12 rivets
OK the short and simple ansewer is no it must be uilt per the plans, ....BUT if money is not an issue you could build the aircraft per the plans and get it FAA approved, then you can make any changes that you wish (so long as it still meets the LSA requirements) so with a RV-12 the wings come right off and you could build a second set with the wings flush rivited if you like, you could use normal rivits on one side and pulled countersunk rivets on the other and just put the wings on your aircraft.
Of course if you have a friend who has a RV-12 with plans built wings who would let you use them to get it approved then you would not have to build two sets of wings. It will add a lot of work and it may just make it to fast.
Good luck.
Best regards,
Vern