Have had a good look at the signaling page, would older sigs such as LMS or GWR sems work to the new standard?You can import older routes, but you'll have the problem that legacy content is not included and if you import it into TC3 you'll need to be sure there are no errors in it by checking it with CMP.
Paul
This would seem to be good platform for other 1960's era routes, like QR, as I suppose road traffic and people would be appropriate for the period.