could the software be developed in a different way and manage this with another technique?
Yes. What I would do in this case, (if you have a program to install or whatnot, but you can't access the Path variable) is just make it so that the binary (program executable) is installed into the
C:\Windows\System32 folder. Then you'd be able to call it from command-line or programmatically, by just
program /option, or
program -o, or whatever it may be.
It really would be optimal to add it to the
%Path% system variable, and if targeting Windows Vista, 7, or 8, you can have it prompt the user to elevate privileges and allow it to access it. But if that's somehow not an option, then you should at least be able to do what I said above.