I did the math last night.
The yard will fit in the new basement in either orientation, so I have plenty of options.
I have been thinking about a slightly different theme though... I love the idea of a "what if" for the New Portage Secondary (aka, the Mule Shoe Curve line). I really want to try out some helper ops and that'd be a good reason.
Windsor St could become Hollidaysburg.
This is, of course, just an idea.
Likewise, I could also just dial up the grades on the NCR a bit. It wouldn't be that unbelievable: the WM ran helpers almost all the way to Baltimore over similar country.