I don't think such an option would be very useful; it would only make the B button act inconsistent and annoying.
Why so? If you want to go to basescape after sucessfull interception, when probably you do it for assembling a craft, better corresponding for particular target assault; if you want to go home after ground mission, probably it will be home of that victorious squad, to examine wounds/stats/vaults/whatever.
Only exception which I can imagine here is playing style, when you have only one active base and rest of all are auxillaries. But in such case vanilla behavior of <B>ase command doesn't suit you either.
So ideally here should be three separate behaviors: default; go to nearest base; go to first (main) base.