This looks like back-to-back ticketing on an explorer! Sure is legal, and you'll actually be travelling both tickets entirely.

The one caveat - as with back-to-backs - is that while legal the airlines will probably frown on this. They often go as far as denying boarding on back-to-backs once they find out what you're doing. You have to threaten legal action etc. As with back-to-backs, get around this by mixing and matching which airlines you are flying, and only put your FF number into reservations after you have traveled.

Otherwise go for it! Sounds like a great idea.