No, don't go there mate. That's an overused, worn-out argument used by people who don't get it. Of course you won't be using legacy programs on a 5" screen. Legacy programs are meant to be used on at least a 10" screen (maybe 8" but for me no). And on an x86 Windows phone you would be using Continuum to drive an external display with a keyboard and a mouse - on a desktop not on the subway. Are you saying Continuum won't work because you can't use a keyboard and an external display on the subway?
When you want to use legacy apps, use Continuum. When you're on the move, use mobile apps. And when the app you want is not on Windows Store, then use Bluestacks or DuOS to install from Play Store. DuOS works very well of my daughter's Venue 8 Pro and I'm sure newer Atoms that will be in an x86 phone will run it better than the DV8.