Of course Federer would still be ahead. What I'm saying is if you trade RGs, you just make Nadal into another less successful Federer. This way, his records will stand for ages.
Think about it. Careers used to be 15 years on the high end (17-32) and only a few of them were slam-winning ages. Now it seems that players can last into their late 30s and win slams, extending that shelf life from 17-32 to 17-36. The extra 4 years is a huge thing, and potentially spells doom for future records, particularly if that can be extended further.
Nadal has probably made his record immortal with 12 RG. Even with a 20 year career, that takes extraordinary skill on clay, a lack of other significant clay courters, lack of injury/fatigue, and a mentality that just won't stop. However, 10 is 2 less than 12 (Next time on TripleATeam says the obvious...), and that means it's that much easier to break that.
Say a new phenom comes in, wins 6/8 RG the way Borg did, by 25. To surpass 10, all he would need is 5 more RG over the next 10 years. Not easy, but with the right circumstances it could happen. Now imagine that even after 6 RG, he needed another 7 to surpass Nadal. 7 more RG over the next 10 years. That's nearly impossible unless the stars align.
I really don't think it would be wise for Nadal to trade in RGs in order to be behind Federer in terms of versatility. He needs to win the GOAT debate on his own terms - surface dominance, not sheer dominance.