First of all, a big welcome back to one of the finest hobbies in the world.
You asked for an opinion on your track plan idea - well, here is mine.
I see a number of typical beginner´s design flaws.
As most of the others have already mentioned, there are areas that are beyond the reach of a normal adult. I don´t see a way how you can work on that yard in the upper right corner, unless the entire layout is accessible from the back end.
A second issue is that you have planned your track way too close to the edge of your layout. Not only will you risk your precious locos and rolling stock being shattered on the floor in case of a derailment, it will also not look right. You should allow for at least 3 - 4 inches to include some scenery.
Most of the action on the layout is on the far end of the layout. Add to that the reach issue and switching will become a nightmare.
Roundhouses are always a nice eye catcher, but just having a turntable and a roundhouse without having the necessary engine servicing facilities does not make much sense.
I see only three spurs for industries to be served, for a layout of this size this seems too few.
There is no obvious reason for the track in the front to meander the way you have drawn.
Your plan does not include any staging facility. Staging is the place where we store or trains. Staging also acts as the starting point or destination for our trains.
A footprint of 16 by 6 ft. is an awful lot of reals estate for a layout, but I am afraid this plan is not making the best use of it.
This may sound very negative to you. I don´t want to discourage you, but a layout is always a quite significant investment in terms of time and money and therefore should be well considered.
Designing layouts is an art, which very few of us master. Although I am an old hand at designing and building layouts, I still have a lot of problems with “filling” such a large space.
What to do?