Once folks get comfortable with and enjoy the guaranteeable 10 net turns' reversibility by either side, if they thirst for more versatility then perhaps increase to a maximum of 20 net fullTurns reversed by player BUT with a maximum of ten individual reversals each AND no more than a dozen (12) fullTurns reversed on one halfmove. A few restrictions to prevent say restarting the round 20 moves in (even though that would cost full reserve) with decreased times on non-reset clocks (perhaps less on the opposing side that did not opt for reversal). In this same vein, perhaps a 'cooldown period' of say a half-dozen(six) turns would be appropriate. Other restrictions could be implemented by agreement based on e.g. progression of the game (piecewise, i.e. moves 1-15, 16-40, 41-preConclusion).
Takebacks allowed (up to 10 net turns)
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The rules are exactly the same, with the addition of one: permissibility of takebacks, up to a certain agreed-upon amount per side (I suggest 10 full turns as a reasonable cap). Naturally in a fair match the number of maximum authorized takebacks and any restrictions concerning them ought to be equal for Black and White; otherwise it is an odds match, not unlike granting extra time for the weaker side (although gifting the weaker player takebacks would offer more interesting and educational rounds than adding more thinking time for a player who lacks the intuition for seeing future positions or calculation abilities to take advantage of this handicap-bonus against a far superior opponent).
There could be different possible restrictions, such as limiting the maximum number of takebacks to five (fewer than max reversible turns), or requiring it happen after opponent's move / start of deployer's side (affecting half turn and maintaining clocking side fair), or returning to only the first 'most original instance' of that turn in sequence (rather than chronologically, or perhaps charging extra halfturn for selectivity on linearity); but keeping it simple would probably be best: the only restriction being total number of turns reversible by either player within the round, be them ten 2ply-deep reversals or one 20ply-deep reversal or anywhere in between (not requiring deployment of entire allotment).
Notation need not be complicated. Something like an asterisk followed by the return-move ordinate optionally followed by bracketly or parenthetically cited turns 'spent' followed by the move executed from that point presuming retraction to same side's play would suffice. So if it is Black to move on move 17, then assuming he had not used any takebacks from his reservoir he could go back to as far as [the the most recent instance of position arriving at ]move 7, which could be notated as 17...*07(10.0)Nc7. The immediately following halfmove, played by White (unless Black missed checkmate-in-1, and had went back to deliver it post hoc, which this example doesn't illustrate in absense of a hashtag or double-plussign <# or ++>), would be preceded with "18." in usual fashion. Presuming White player had takebacks in his reservoir, he could go back one or more turns, but to a position correlating with initial move 7 down (to opening move0 if he so chose, having spent fewer than two takeback turnz prior to move18).
Naturally this is more conducive to an easily adaptable online-based platform (allowing for representations of superseded sequences via 'sidelines' and flowing graphics for layers) or LAN intranet (to ensure no cheating), although achieving this type of play dynamic over-the-board could be doable as well albe cumbersome, involving freezing clocks and iff necessary by contestion arbitration (availability of an extra board&set or more might assist).