Well, how often would you shoot a wedding at F2.8? Not very often, I would assume. You would shoot at probably no wider than F4 anyway. In fact, you'd be more likely to shoot at F5.6-F8 anyway and perhaps with a flash. . . the RF645 has a flash too that you can buy.
I took the RF645 out at night (very low light) with delta 3200 (at 1600), so you could find some Neopan 1600 and be perfectly fine in a decently lit church.
This is a handheld in Paris, Delta 3200@1600 :
http://www.shutterflower.com/street scenes gallery/pages/passage-in-parisRFF.htm
VERY low light. You'd surely have better light than this.
The Neopan 1600 is magnificent B&W 1600 ISO film. . . i should have brought that instead of the Delta, oh well.
If you only shoot B&W, the Epson 3170 is very decent for prints at 8x10. . . not great, but you'd have a hard time finding a printer that would actually make use of more resolution. THe only gain you'd make with the 4990 is DMAX. But how much do your negs really have?
Just ask yourself, how often would you shoot a wedding shot at F2.8? With manual focus, probably very rarely. You will probably be looking at 1/60 to 1/125 indoors with 1600 ISO film @ f4, assuming low light. But decently lit, probably twice that or more. Honestly, I can't imagine any reason that this camera would not be perfect for weddings. I shot my sister yesterday, for a comp card, in a decently lit (no lights but for cloudy sunlight through large windows) Westin lounge, and things were just fine at 1/125 f5.6 with 400 ISO film. You'll be more than fine.