At first I want to thank you all for your help.
The early BN idea is very attractive because I already have a GN GP7, a GN U25b with sound (or28?) and a BN GP30. I didn’t know that BN used (at least for a little time) it’s predecessor’s locos with their original schemes. I have to make a research on the net.
CP is also attractive for me, I also didn’t know that they bought US railroads (or no?).
I also have seen photos of CP locos with BN locos together.
I liked your thoughts for NS, but I wouldn’t mind if I used it less for the start.
Shared track is another idea I’ll consider, especially if I’ll find something that includes schemes I alreay have.
Hard to find locos and schemes are somehow difficult for me, as I buy from UK and variety and supply are limited. If I buy from US I have to pay a lot for customs and posting, except for items marked as gifts.
I know the famous Fallen Flags site, but it’s a little matter of luck to find photos of mixed schemes between these zillion photos.
Also I have to think about scenery and type of car as you suggested, but think a small town could have a variety of freight cars sent to it.
I forgot to say that the layout will begin as a 2 or 3 modules modular layout (will be part of a new and first in Greece modular group, following the FREMO design – I’m the only at present with US theme).
I will use it as a simple switching layout in my home (except for meetings).
Time and place permitting I will expand this with more modules or make it part of a bigger layout.
I will make 3 or 4 small industries (or suppliers) in a small town and will have only small freight trains.
I’m in the designing of this, and if anyone thinks it may be of any interest I can post a drawing here.
So, I’ll study again your suggestions, will research the net and look again in some books I already have. If I decide a particular road, I’ll have to buy more spec