New build M&GN C class

Or sold, as has already happened with one of the unrestored IoM carriages, which has gone back to the island.
Not long ago the Bluebell Railway also sold a loco (USA Tank 30064) - a very rare occurrence for them even though they have loads more out of use.

 

Given that standard Midland 4-4-0s and 0-6-0s were provided with only minor alterations to both S&DJ and M&GN, a replica build could in theory be decked-out in Midland, S&DJ, M&GN, LMS and BR liveries without taking too many liberties. But I think it would still be difficult to find enough support to build such a replica. Most new-build support seems to be generated for large, named express locos from the mid-20th Century era.

The M&GN did not have any locos as impressive as the S&DJ 2-8-0s, two of which have survived. When the LNER took over operation of the M&GN in 1936, it took a dim view of the loco stud. Most were withdrawn over the following few years, leaving only a few shunting tanks to reach BR in 1948.

The 40 members of "Class C" Johnson Midland 4-4-0 had been the principal M&GN passenger motive power from the 1890s until 1936. Unlike their counterparts on the Midland/LMS, they were not modernized with superheaters or piston valves. The M&GN also had 15 4-4-0s of "Class A" inherited from its predecessor, the Eastern & Midlands Rly. These had been designed and built by Beyer Peacock in the early 1880s and bore a strong resemblance to the 4-4-0s built by William Adams during his earlier years on the LSWR. I am sure that the North Norfolk Rly will be looking towards Swanage with a view to borrowing No 563 for a gala.