why not just buy a cheap 2ndhand guitar for playing in church? If it gets damaged, it gets damaged. (though you may as well fit lighter strings too)

I have one song in which I tune the top E string up one semitone. It never occurred to me that I might be damaging the guitar in any way - it's only one song after all, so it's only in that position for 3 minutes at a time (or, when practising that particular song, say 15 minutes).

Surely back before the advent of digital tuners and the like, musicians were frequently playing guitars that were often a bit sharp? I mean, I find it hard to believe that itinerant blues musicians were all that bothered about whether their tuning, which would inevitably have drifted from concert pitch up or down, was damaging their guitar...