I'd love a new anime expanded like PGSM, but not an animated adaptation of PGSM.
They could keep some of the elements such as everyone having the power to disguise (they could use an app now, apps downloaded from the Moon Tower, lol).
Fleshing out Motoki was great, but I feel like they merged him with Umino, Umino should be brought back, same for Unazuki...while they're at it they could even tie in 90s anime characters to fill in where needed (Uwara, Yuuichiro)
I'd want it more tightly plotted with more interesting Youma.
Basically, an amalgamation of what has come before and fresh new stuff. If they could keep each arc about 26-52 episodes, even better...and maybe even add filler arcs that were shorter based on the musicals.
PGSM wasn't perfect but the pacing was better than a lot of the other stuff we've had and the more mature themes presented with Rei's father and Minako's disease would keep older fans invested. As long as it doesn't get made by the CW. ;p