The FP-45 and F-45 have very few differences and could easily be done by Sunset, just like all the changes on the FP-7's they have done.
Unfortunately the FP45 and the F45 are significantly different in length. So, as with an F7 and and FP7, a totally different tool is needed for the shell and the frames are different lengths.
The MTH model was introduced in the premier line in the 1990s and was even offered in 2 rail before being demoted to "Scale King." An updated model with the detail of the current MTH SD45 would be most welcome. The Milwaukee FP45s did not have dynamic brakes and it would be nice to see some new tooling with the flexibility to model them that way.
An accurate F45 model with the correct length would also be nice to see on the market. GN, BN, ATSF, WC, MRL and Suzy Q fans could finally get real F45 models. I'd probably be in for GN, BN and MRL and might even get a yellow bonnet ATSF unit to model the period right after the BNSF merger (sorry to mention that Matt) when all sorts of 645 power was sent to Intrerbay and worked over Stevens Pass.