Yes, I think you are. Basically if you build an RPM, it does the ./configure; make && make install. Geerally FOSS packages default to /usr/local and distro's configure them to be rooted at /, /usr, /opt whatever.
So in fact you ought to be able to be able to build Gen++ packages, rooted at a different place than Gen, and select which implementation you use by traditional means $PATH & environment.
Opening up openSUSE 11.2 Software Package manager, and I find :
So perhaps Distro's with good package managers are not the problem at all.
Whoops I just installed python3 without really meaning to, expecting it to tell me about other packages it would require installed to with it.
I have both installed, guessing it'll be python3 :
Python 3.1 (r31:73572, Oct 24 2009, 05:39:09)
[GCC 4.4.1 [gcc-4_4-branch revision 150839]] on linux2
Type "help", "copyright", "credits" or "license" for more information.