Trouble Assigning Units to a Custom Scenario

I reckon it depends on how large or small you want it to be & what you have in your collection. I also think you are trying to create an Order of Battle by your question, how do you assign the units.

I use as my Rule of Thumb for size of units & attached support, 1 infantry equals 1 squad, 1 tank is 1 tank & 1 ART/ATG is 1 gun, 3 squads is Platoon, 3 Platoons is a Company, add machine guns & other support weapons as desired & do the math upward from there. ART/ATG, 3 guns are a Platoon in my design, 3 tanks are a Platoon.

From your list, I would say the band is expendable as are a couple others of the "Specials". Build Combat Formations & give it a go & please let us know how it plays out.