Scale Diesel/Electric-45 Ton diesel switcher. Incredibly small engines, these would be able to go around the small Superstreets curves they sold under the KLine name
Lionmaster-A traditional sized version of the Virginian Ry. 2-8-8-0's. These would be able to utilitize a USRA mike body. (See 1967 issues of Railroad Model Craftsman)
Scale freight-1860's era cars, beyond stock car, flatcar.
Scale Passenger-ditto
Traditional Locomotives-A new 4-4-0, an old time 4-6-0, a 4-6-0 or 4-6-2 made using the pilot from the 1666 and the body from the 2026, a 0-6-0 using tooling from the 0-4-0, and a proper K4 type using the 675 tooling, in 2 versions: traditional Brunswick green and in a festive shade of red, with a silver (or gold) smoke box and green lettering. Both would be capable of linking up with an iPod or the like to play Christmas carols (or whatever other music someone feels like).
Traditional Cars-something semi new, that hasn't been issued in the past 20 years or so.
Accessories-an operating water tower and the 356 station
Track-tubular 027 profile, in 021, 027, 031, 036, 042, 048, 054 sizes.
Power and Control-sanity
What If? (the off the wall category)-A ATSF 2-10-10-10-10-10-2, like the one shown above, which was published in the early 1950's era Trains magazine, and some realistic prices.