I am trying to design a plan that I can take to a steel supply company like Mueller or someone local that has a 40x60 footprint with a 15 foot lean to on the 60 foot side. It will be a 16 foot tall building with 14 foot roll up doors. I want to add a bedroom and a bathroom and possibly a kitchen, small living area that could serve as a man cave and possibly a processing area for deer, fish, etc.

Does anyone have stuff they've done in the past and what they would do differently? I'm curious if I should do a loft type of layout or if I should do an L shaped building with the small part of the L be the living quarters.

This is actually becoming quite common. I am sure any of your steel building dealers could do this and have plans already that you can look through.

Here's what I'd do:

I would stick to rectangular building. Once you decided on how many rooms and bathrooms, google apartment layouts and just pick the best layout. Between the shop and the cabin, set aside 10ft by the width for an enclosed shop room that you can also add AC to. Also, I would recommend adding a storage loft above the room with steps up to it.

Check out qebuildings.com for some really good prices on red iron kits(IMHO) based on where I live in North Mississippi. And the 40x60 size you are looking at is the best price per sq.ft. when comparing the other sizes.