You probably won't get many positive comments from this group on inkjet printers!
I use the Mamiya 6mf, but only in 6x6 mode (you can always crop it yourself, why bother with the in-camera mask, it's an unnecessary hassle and gains you nothing). The Mamiya is a *great* camera. You will certainly enjoy it for landscape work. Its weakness is in portrait work, because the lenses don't close focus sufficiently for nice tight portraits. But for street and landscapes it is a great camera, especially if you are going to hike. It is *very* portable.
Regarding scanning: (APUGers, move along please - there is nothing for you to see here! :-) ) I use the new Canon 9950F. All the images in my gallery were scanned with it. It is very cheap, and for a flatbed, does a great job. It isn't perfect, but once you get dialed in with it you can get solid scans (worthy of web or digiprinting). It does scan through glass, so you sometimes get newton rings, but a rescan usually solves that problem. The supplied software is not the greatest - convenient, but not sufficient for fine art photography. Get VueScan, it is downloadable, has a free trial version, and is about $79 as I recall for a full license. With VueScan, the Canon is a fine scanner for normal use. If you have an image that you just must have a higher quality scan of (either bacause it is just that good, or has density issues the Canon can't burn through), just get that one image drum scanned at a commercial shop. You'll save tons over what you'd have to spend if you bought your own Imacon. OTOH, if you have the cash, an Imacon scanner would be great to have!
Film: I use Velvia and Provia. They say Provia scans better, but I haven't been able to tell the difference to date. I think it is more a preference regarding how you want to interpret the scene. Velvia is the most saturated, Astia the most neutral. You should probably shoot all three and make a judgement call yourself. They are all fine quality films, and no one will be talking behind your back about your choice regardless...
Regarding printer choices, you might want to go to photo.net to ask. This group of folks would be happy to talk with you about enlargers, contact printing, alternative processes, etc., but does not discuss digital printing. This is by thoughtful choice.