I struggled with a similar conundrum last summer and thought happiness could come if I invested in a kickin' basement sim setup. While out on a long run, I met my ppl CFI for the first time since packing the handheld Magellan 315 with the flight bag into the attic a decade ago. He mentioned a local opportunity in an M20E partnership and that pushed me back to get a medical, a lengthy set of refresher lessons, and a BFR in the old rental 172s rather than sink money into a VR rig. My experience and mission is similar to yours (s/Vineyard/Block Island) and buying into the small partnership so far provides freedom from the constraints of rental aircraft but a very helpful cost sharing model for any hefty maintenance expenses; we'll see if those two theories hold...
I highly endorse Hank's suggestion to complete the complex endorsement immediately after getting current and wish I'd heard that advice 6 months ago. The partnership needed to change insurance companies for me and I'm footing a hefty first year incremental with specific restrictions on CFIs to train me (required number of Mooney hours).
...and there's a Mooney Safety Foundation PPP in Nashua in early September (as recommended by @Oldguy to get your Mooney 'Masters'). I'd consider attending myself, but doubt I'll even have my 'high school diploma' by then so it might be too big of a leap.
If you identify a Massachusetts Mooney-specific CFI (or if you're serious about selling your VR rig), send me a PM with details; I'm still looking for either.