Waaaayy back in the 60's, (read by me in 1981 after his death in 1979) Lawrence Revere did a study of one deck without 5's and without Aces. In a rule-set with a 0.02% House Advantage, Revere reported then a gain of 3.02% by removing all four 5's.
If those figures are even close in today's games, then removing 24 Fives from a 6-Deck shoe with a rule-set that provides a 0.52% House advantage would yield a 2.5% Player Advantage.
Note that each Five in a single-deck game are worth more *each*. And that to have an advantage in the 0.52% House Advantage game, there would need to be a shortage of 5 Fives (+0.10%) considering the 6 decks. With better game-rules, fewer than 5.
The bigger caveat is that there is not also a shortage of Aces (considering the original study). But consider that if a 5 gets burned in the 6-decker, that the H.A. drops from 1/2% to 3/8%. And in my local game with a 0.33% H.A. the game improves to about 0.21% H.A.