Only argument I can see against expanding the loadouts of the 51 and 38 would be if it imbalanced the game... although I don't think that it would do so. If people are willing to impair the performance of their plane I think they should be allowed to carry these even if they were uncommon in WW2...
I almost guarantee 10 HVAR's and 1000lb bombs were not carried. Find a picture, then sure.
6 HVAR's and 1000lb bombs now has photographic proof, and I'm willing to drop that particular issue. But based on the lack of photographic evidence was VERY rare. Now the 10 HVAR's looks to have been very rare all on its own, and was likely never carried with 1000lb bombs.