Computer+good interface+midi foot controller+full 400$$native(+maybe daw license) isn't cheaper than Helix lt! Sorry, but I don't see any advantage to do this. Also, you'll get a super fragile rig, cheap computer(understand non heavy duty ex.toughbook) are rarely build to last, USB connection are easy to broke and sensitive to humidity. Also, bigger latency, no sound adjustment on the fly (Helix interface is really nice for that). Even if you already own a daw, interface and your computer, you will need minimum to spend 400 for the license plus 150 for a cheap midi controller Beringer who might give you headache to program and work. For not even the double, you get an heavy duty interface/controller with the software and the computer to run it, without issue and latency and a super slick and nice interface! Man, who want a painful to use Helix!? It will work for sure, kinda.
Also, you can always resell your Helix if you want to change, but you can't really resell your software license.