My pick would absolutely be Stepney, as it would be a cost effective and more universal way to celebrate the 75th anniversary of the franchise. Stepney has a wide appeal amongst modelers in and outside of the Thomas fandom, and is still beloved by several modern generations of Thomas fans. His release would also inspire several people who do not normally purchase Bachmann products to start their own Thomas and Friends collection.

Ryan is still a good model nonetheless but his size and details will make him a very complicated and expensive model to produce. As someone who has spent hours cad designing models of Ryan I can say with confidence that he would take a lot of time to design and mold due to all the complicated tubing, shapes, etc... He would be better suited for after the 75th anniversary.