[davidmanze]

Why not smaller and lighter stuff?
https://www.f16.click/gear/fujifilm-50mm-f2.html

  IQ  ....... low light levels inside the church favours FF ....... there will be a percentage of portraits (DOF) ..... inside shooting without flash ...... I'm sure Fuji could do the job ....... but why? FF is better..... the size between say a Z7 and a Fuji body is not really significant ....... the M4/3rds system sweet though it is, just doesn't look pro ...... how would it look if one of the guests brought along his own D850 /Z7 with a range of lenses and gets better images?
 ...... this is nothing to do with DSLRs vs ML ...... quite the contrary, if I was shooting weddings I would use a FF ML body, for the AF coverage and the silent shutter, which I think is essential these days for weddings.