I have a reverse loop on the C&S portion of my layout which is bounded by a stub switch at either end.
Part of me wants to kill two birds with one stone and use the stub point-of-switch as the isolation/transition to the reverse loop. This would also give me the longest-possible reverse loop.
But another part of me thinks putting two possible failure points together is a mistake, and it would be better to have isolation gaps a foot (or so) back from the stub switch for the reverse loop. The reverse loop would be a bit shorter, but still at least as long as my longest siding.
(Scale is HOn3. I have a second reverse loop, but it's on the D&RGW side where it's bounded by a point switch, so it will require a separate isolation gap either way.)
I would put them back a bit from the turnout. Don't know if you are using DCC or DC and if you are automating the reversing
of polarity. That might also be a consideration too. There are several good solutions for DCC reversing sections that I have used.
I, too suggest you locate the isolation gaps a few inches past the turnout. While I cannot state a reason not to double up, it will make trouble shooting easier as the reversing section is isolated from the switch. Also a wise man long ago suggested that the train length be shorter than your reversing section.