My first layout was 18 years ago....two 4x8 sheets of plywood in an L-shape. I used cork roadbed,laid all the track, wired it into 7- blocks( before DCC became mainstream) , built a switch-panel with trackplan and dpdt turnout contro-switches for each of the 15 turnouts and started on the scenery(all took about 4 months of time). And then realized..1) it was going to be multi-year job to get it anywhere finished, (2) realized I didn’t like the trackplan (3) it just wasn’t inspiring me. So I tore it all down and built a switching plan (pic attached) designed by Matt Chibbaro in his book Model Railroading in Small Spaces. This was a really nice little 5ft. x16inch layout that I was able to complete to a high standard very quickly, about 4 weeks....and it offered some nice switching possibilities. Both layouts taught me a lot about various subjects,carpentry,trackwork,wiring etc., and the first one especially helped me gain confidence in wiring and electrical work. So my experience would be that actually having a completed running layout actually can be the food that drives one to continue in the hobby. Over-reaching can be frustrating to the point of actually driving one out of the hobby. I think that you learn what you actually really like and what your preferences are by building to a fairly complete level so better to start smaller but have a good plan that allows for easy future expansion if you end up wanting to go bigger down the road. So I would say...take a manageable portion of your plan above, say something in the order of 12 sq.ft. and build it to a fairly complete level, running and scenery wise. But design it and build it so you can add sections easily in the future.