This is really rough, but I'm sure you guys can really help refine it. Anywhom, I want to do an army list which can be used to reflect all SM's Pre-Heresy, but it's up to whoever uses it to not be a Bar-Steward and be unfluffy.
Here's the basic idea: Squads can be anything from 5-20 men. Their special and heavy weapons options are more limited than those in the SM and CSM lists. The basic Troops squad will have the option of either CC(eyness.........) or shootiness.
Marine snipers are an option (either Heavy Support or Elite). I figured this would be alright, seeings as Pre-Heresy, SM's were the common army of the Imperium, and would be designed to operate under many circumstances, as opposed to rapid assault.
Specialised squads (Devastators, basically): Either have special weapon squads as an option, or us the IG codex as an example, and create anti-tank or anti-personnel combinations, which would be seperate choices.
Jumppack troops: Expensive. Very Expensive.
Bikes/ Jetbikes: Same as the SM entry, but can be upgraded to Jetbikes for a smallish price.
Rhino's are the only transport option. Predators are v. common, Land Raiders are slightly cheaper than 'now'.
Maybe use IG vehicles, which have been around forever.
Another idea I had was to change the force organisation guidelines to work like Fantasy, making people choose more basic troops in order to get the better stuff (or the 2nd ed. 40k percentages thing could be used.)
Sorry it's sketchy, but I need help, and thought I'd pitch it before it all flees from my mind.