The fact that HO Scale is getting Rebecca, a newly-tooled tender engine, really opens up the possibility for Hiro, or Flying Scotsman, but if another new tooling isn't viable at this time for HO Scale, then recolors would be another way to go, like Sidney, Fernando, or Green Salty. Regarding the Mainland diesels, they may not have much character, with only one being named (Ulli), but it's really hard to paint that livery when modeling. Bachmann has the tooling to make a red Mainland diesel or two. They could be called "Mainland Diesel #1" and "Mainland Diesel #2". Same livery, but different faces. They would make good shunters for a layout. Their faces can be swapped with other characters of this tooling when modding. They're making Beau because they have his tooling, and he was a one-off character. It would be interesting if Fernando, or the Mainland diesels could get their first official pieces of merchandise. One of the latter could even use Fernando's face.
Although there's a fanmade CGI BoCo, it's still not likely Mattel would approve of BoCo because he never officially returned in CGI. Splatter and Dodge were going to return in Day of the Diesels and The Great Race, but both times, they were dropped. Although they'd use Diesel's tooling, they haven't been relevant in two decades.
The next N Scale engine has to be Henry. He would share the same chassis as Gordon, minus the trailing wheels. Graham Farish toolings can be used for the Express Coaches.
Although there's a fanmade CGI BoCo, it's still not likely Mattel would approve of BoCo because he never officially returned in CGI. Splatter and Dodge were going to return in Day of the Diesels and The Great Race, but both times, they were dropped. Although they'd use Diesel's tooling, they haven't been relevant in two decades.
The next N Scale engine has to be Henry. He would share the same chassis as Gordon, minus the trailing wheels. Graham Farish toolings can be used for the Express Coaches.