I’m guessing this is an island design. Otherwise some of your yard trackage on the inside of the oval would be very hard to reach. Access hatches are a great idea for maintenance purposes. Shouldn’t really be involved in regular operation. I drew my layout on graph paper over 30 years ago. Until you see the benchwork up and track getting laid do you realize what it’s going to look like. Usually not quite as big as you think it looks on paper. I had way to much yard trackage drawn in given the space I had. Mine has been tweaked over the years as interests change. But not anything major.
The space you are given can’t change as far as how much benchwork you can put in the space. It looks like you want large curves and an oval design. I think I’d build the benchwork to fit the space and layout the 2 larger ovals of track with maybe a few turnouts in place and just start running some trains. Build or buy the structures that are must haves and figure out to incorporate them into the layout. It’s fine to try and design the perfect layout. Trouble is you can’t build it overnight and in the process of building. You will get different ideas as you see the real layout take shape.
