Aluminum vs Stainless is one of those hot topics right up there with Glass vs Plastic, Secondary or Not, etc. Be prepared.
When you boil it all down, though, it seems that Aluminum is fine, you just need to be aware of a couple of things. Before you brew in aluminum, you want to "passivate" it. Just fill it completely with water and boil for 15 minutes or so. This builds an oxide layer that'll keep the acidic wort from reacting with bare aluminum. Once you've got that layer, you're good to go. Also, be careful when cleaning that you don't scrub off that layer or you'll have to passivate again.
Finally, most of the fryer setups have a 7 or 7-1/2 gallon pot which you may think has "plenty of room leftover" but is not really the case. That's about the minimum size pot for a 5-gallon batch full boil. When you take into account the extra you need so that you end up with 5-gallons, hot break, etc., you'll need to keep a pretty close eye on a pot that size.