Very different contact points and swing mechanics make this unreasonable at the top end.
My take on the slow death of the one-hander:
1) As courts slowed down and enabled movement to play a bigger role in the game, the advantages of the two-hander came to the for (control, returns, defensive ability) and the advantages of the one-hander (variety, spin, power, usually easier to slice and volley) fell away.
2) As players have become taller the average bounce height has increased making a two-hander a better shot to handle the extra height. Isner's serve is not hard because of the pace, but because of the BOUNCE. Ditto on Rafa's forehand.
3) As others have mentioned, youth results are heavily emphasized now - parents want results immediately, and few are willing to stick out a longer, slower path to improvement that the one-hander entails.
4) Grip change. As the forehand grip has become more extreme in recent decades (more western grips) the one-hander has become more difficult to change to in rallies. Fed only goes from eastern which is a much smaller change, but players like Kohlschreiber and Almagro ended up using the same side of the racquet on returns given how extreme their grips were. Works for return but is a hassle during quick rally exchanges.
5) WIth respect to taller players, having long limbs makes the two-hander an easier choice for big guys; you want control as you get super tall
Just wanted to comment on a few of these:
1) I think what happened to the 1HBH has to do with the style used by players from '90s and before. The 2HBH was much better for slower court, movement based tennis than the continental 1HBH. It wasn't until players like Kuerten, Haas, Robredo, Gonzalez, Fed, etc. pioneered the modern eastern/semi-western 1HBH. I think due to the 1HBH's evolution, it's even more of a slow court shot than the modern 2HBH since it has an elaborate takeback and requires more time and movement...which might be why the stronger 1H'ers back in the day were fast-courters like McEnroe, Becker, etc. but many of the strongest 1H'ers today are best on clay. Wawrinka, Thiem, Tsitsipas, Gasquet, Kohlschriber, even Musetti are examples of this. Even Cecchinato, who's just outside the top, has an amazing BH. Only current 1H'ers I can think of who are best on fast courts are Fed, Shapo, Lopez and Evans, but Evans slices like 80% of his BHs and Lopez hits topspin prolly once a match lol.
2) You're on to something with that one. The 2HBH seems to work way better for taller players, and it's still better for the RoS.
3) SO true. On top of that, the coaches don't want to put in the effort to differentiate their training/drill regimen to accommodate players that aren't righty/2HBH. I've dealt with this for as long as I've played. Coaches would act so inconvenienced by my leftiness whenever they'd have to change their drill and ball feeding setups for me. Oh, and don't get me started on how they dealt with my transition to a 1HBH. Now things tend to go pretty smoothly since my current coaches tend to focus more on my tactics than my strokes, and I've seen a marked improvement in my strokes over the past few months.
4) Interesting observation. I've seen Almagro talk about this with the Top Tennis Training guys, and noticed Kohlschriber doing this watching one of his old matches. Most 1H'ers today have semi-western FH's and eastern BH's, except Tsitsipas (eastern FH), which isn't too hard to switch to either. IME switching from sw FH to eastern BH is easy for me, but I see how it's a hassle switching grips from western FH to eastern or semi-western BH. Way easier to use the same grip at that point.
