It's all out there!
P:48 Flextrack
Jay Criswell provides also all kinds of super detailing parts for your right of way
https://right-o-way.us/catalog...20Track-all%20guages
P:48 Turnouts
Bill McConnell does build wonderful stuff, very nicely stained ties.
http://www.oscaleturnouts.com/...uts%20Information%20(3-1-20).pdf
Brad Strong can build you even P:48 double slip switches, I have just ordered one to try it out. Not on his website, just ask!
Hand laying your turnouts is easier than ever before using Fast Track's P:48 turnout jigs and tools
https://www.handlaidtrack.com/fixtures-p48-turnouts
As much as layout space is concerned, that is a given fact that we all deal with but it has no impact on the decision of track gauge. In fact, it was never easier to choose to model in P:48. Steam locomotives being the only thing that you might find a reason to carefully overthink the migration. Diesels can be converted far more easier. However, track is not a concern anymore.
Sarah