Ideas for a Freelance Model Railroad

One of the things I've been thinking about lately is what type of railroad I want to build when I decide to go big and make something larger than a 3-foot shelf layout, I'm talking at least a 4' x 8' layout in my basement. The problem I have is not knowing which prototype railroad to model. My ideal layout would be based on the Detroit & Mackinac, but there is definitely some degree of limitation that comes with a railroad like that. I want to have more freedom than just trying to replicate something in the real world. That leaves me the option of coming up with a freelance model railroad.

Doing a freelance railroad opens up all kinds of possibilities, everything from custom painted locomotives and rolling stock to unique structures and scenery. I know I'm just getting started in all of this and have a lot to learn, but I think it would be a lot more fun and enjoyable to create something of my own. I already have a lot of ideas in my head for different industries and locations that could be part of a fictional freelance model railroad. Here's some basic info:

Railroad name: Michigan Consolidated (MCON)
Location: Michigan
Era: 1980's - Present Day (Diesel Only)
Possible Industries: Automotive, Consumer Goods, Manufacturing

An example of some real life industry supported by rail in Michigan (Chrysler Assembly Plant)

That's a pretty good start at setting some parameters for my future long term layout. For the short term, I'm thinking I can work this into my office shelf layout project and come up with something along those lines. I'm planning on taking my SD40-2 project and making that my first custom locomotive for my freelance railroad. Beyond that I have an old Union Pacific SW1500 and Norfolk Southern GP50 that would make for some additional locomotive customization practice.

Before I can do anything with painting these locomotives with a custom scheme, I need to come up with said custom scheme. I'm working on some ideas now, nothing too complex, and it's coming along nicely so far. I'm hoping to have some ideas ready to post here soon. Until then, I will continue researching what I want this freelance railroad to be and hopefully get a better start on my office shelf layout with this new theme in mind.