The nice thing is, that with an adapter, it can use M42 lenses keeping their automatic diaphragm (it activates the pin in the lenses which have them), making it essentially a 100% M42 camera as well.
While I slightly prefer the Spotmatic (and am still looking for a mythical Spotmatic modified with a Rollei mount), in your case, I'd definitely get hold of an adapter (they're usually fairly cheap) and give your Rolleiflex a try.
Another advantage is, if you get several adapters, your M42 lenses effectively become bayonet mount lenses, albeit still with stop-down metering.
The Rolleiflex I mentioned in a recent post is the SL35-E, an electronic and AE model which was notoriously unreliable when it came out, but surviving working ones (the ones that were "good" in the first place or were properly repaired) can be nice and reliable cameras. Personally, I find it handles quite well, better than the SL35, despite my general preference for 100% mechanical cameras.
BTW: essentially the same mount and same ability to use M42 lenses via an adapter.
The one(s) I mentioned with the built-in motor and inchangeable magazines are the SL2000F, 3001 & 3003 (also essentially the same bayonet mount).
The Rolleiflex option for using M42 lenses could be quite good, also because you can pick up some Zeiss lenses which can fill some FLs where M42 lenses don't shine or where the Zeiss ones are especially nice for some reason.
While a few prototypes of the Rolleiflex 35mm SLRs had M42 mounts, the production models all had basically the same bayonet mount, but with a few tweaks over time to allow full-aperture metering and displaying the chosen diaphragm. Basically all the lenses will fit all the cameras, but will lose full-aperture metering in the "wrong" combinations.