So I found a stripped-down early-aughts Giant Sedona frame by a recycling container (Tin and Aluminum). (For those concerned: I've already checked the serial number, and if anyone's missing the bike, they haven't reported the number, at least.) My friend really enjoys mtb'ing, but his bike got stolen a while back and he doesn't have money to throw around, so I was thinking of building it up as a mtb. Maybe mullet it up with a cheap disc up front and canti's in the back and as big of tires as it'll take.

Anyone know if this is a particularly bad idea with something like an aluminum hybrid? The ones from the early 00's seemed to lean more toward mtb than road bike, and this one definitely has mtb geometry. None of the other parts are present, so it's kind of a blank slate. Thanks!

Check the frame/fork if it will fit 2" 29er rubber first. If it doesn't, the only off-roading this bike will be doing is simple crushed stone trails.

Why does it need to be a 29er?

Bikepedia says that the early-00's models came with 26" wheels and it doesn't have a fork with it, so I kind of have a choice there.

Btw: if anyone knows of the possible owner of this bike in Iowa City, drop me a line on this site.

I had a Giant "hybrid" from the late nineties that I picked up at a yard sale. If BikePedia hadn't catagorized it as a "hybrid" I would have sworn it was just a rigid fork mountain bike with 26" wheels. I'd move forward with the project, but I have two comments:
Not having the fork could be an issue. The geometry of some of those bikes will not work with a suspension fork. I found that out the hard way when I modified a late 80's Nishiki Ariel. So I'd resolve the fork concern before sinking money into the project.
Also you mentioned going with a disc brake up front and canti's on the rear. That will require mis-matched brake levers. You might find it better to mate the disc with V's on the rear. Several entry level MTBs were marketed that way.

Since it is a budget build I would be happy with 26" rims and EQT. The Canti's in the back and Disc up front make good sense. I remember in the early 90's riding ridgids everywhere. Tires back then were 1.8's, the entry level mountain bike was just an overweight Hybrid. Take care of it and don't get too crazy. That sucker will take you places.

Thanks for the advice! I have access to a ton of used parts (and an extra disc brake from an upgrade), so money shouldn't be an issue, but the fork sizing could be. Also, when I say "cantilever" I mean "V-brake." Always mix them up.