@devnulljp to echo @Chet 3 experience, the S1 will not have nearly the projection or disbursement of sound that the L1 MII with B1 or B2 would have. You can plug in a ToneMatch into one of the channels of the S1 just fine. However, the ToneMatch will need a separate power source so not sure that is solving your issue with playing in rural areas with questionable power.
If it’s a small, intimate setting, perhaps a S1 will do, preferably 2 S1s in your case. Several folks on the forum use 2 S1s with a battery powered Behringer mixer 1002B so they can run all battery powered in what I think sounds like a niffy setup. With 2 S1s you might be in better shape, but it still wouldn’t provide the extensive coverage from a L1 setup.
In the articles that ST has mentioned, there is a suggested Honda generator which I believe is street priced at $1000 or so. I know this is probably far out there, but if you do enough of those rural outdoor wedding gigs, you might just be better off getting or renting that sort of generator and continue using your trusty L1.
You may still want to get a S1 or two for smaller scale gigs, which is what I’ve done where our L1 would be overkill, but not use it as a stand in for the L1.