Use default browser when FF Portable can't be started

I'm not sure where to post this but I'd like to make a feature request.
Sometimes Firefox Portable refuses to start because there's a local copy of it runing on the machine. The problem is that some portable apps use firefox portable if it's installed instead of using the default browser.
I'm wondering if it would be possible to launch the webpage passed trough the parameters in the default browser on the machine or (If it's possible) in the local firefox installation.
Instead of showing the regular dialog box about another instance of Firefox, also tell the user that he/she can launch the default browser instead. Also tell the user about the risks and then display a 'Yes' and 'No' button.