I have looked at Atlas's Ho-8 ( Super Pretzel )
I think most people are too hard on most Atlas plans, but in this case I agree, the HO-8 is just a mess. It looks like one should be able to run three trains simultaniously, but because of all the crossings usually just one train can move at a time. I would not recommend any further consideration of that plan.
and HO-16. Are these decent style plans to start with realizing there will be modifications and expansion down the road?
HO-16 is actually where they took an "original" toy train like plan and expanded it. In the original book,
HO Track Plans for Custom Line Track, this plan's chapter is called "Expanding a 4x6 in to a real railroad". It is for running three really short trains and has the operational limitation of being flat with a crossing. It does not say "hauling coal" to me at all. Are you hauling coal in 1950s or modern day? for 1950's look at HO-33 or HO-20. Either of those could be adapted especially in the space you have available and KNOWING that expansion will happen.
We are thinking on a coal hauling theme ... I am considering this a learning experience before moving on to more complex operations so I do not want this first part to be real complex. Any thoughts and ideas are appreciated.
Modern coal or historical coal? There will be big differences in both the trains and trackwork. Most of the Atlas plans were originally developed and published in the 1950s and assume 40' and 50' freight cars and when a Trainmaster was a monster locomotive and a GP9 or F7 was normal.
Modern coal facilities do have big train loops in them. The coal trains are never broken up in yards, but remain together as a unit train.
Here is a 1930's coal hauler (2'x8' in N-scale) by Texas Zepher on another forum. The concept could easily be addapted to HO scale. Notice how the mine is up on a hill and the main line runs through the valley below. The mine has its own locomotive that moves full coal cars down onto the main spur (dog leg one) by the main line and picks up any empties to take back to the mine. The locomotive has its own track up a the mine, that short track at the leftmost top. The main railroad's next local train picks up the full loads and takes them somewhere off layout (the hidden tracks in the back). Likewise the main railroad returns empties for the mine train, as well as switching the grain elevator and stock yards. The Main railroad also has passenger and through freights rumbling through all the time (once again to and from the hidden tracks in the back).