pylauncher should detect existing installation of IronPython in a way similar to cpython. The registry entry used by IronPython is different: SOFTWARE\IronPython instead of SOFTWARE\Python\PythonCore.
The detection of 32 vs. 64 bit should be based on arbitrary IronPython naming convention:
- ipy.exe - 32bit
- ipy64.exe - 64bit
I will have to check, but very likely 32bit version is the preferred one.