Current layout is on a 4x8, but I think I'm up for a new build over the course of 2023. I'm starting the transition to Scale/Legacy, and have plans to start bringing on some O54 minimum equipment...so that means we need a bigger layout! 
"Somewhat Temporary" likely means at least 2-3 years of use, in the crappy basement, until said basement gets finished and we dedicate a space to a larger, and more permanent layout in the future.
The objective is mostly running trains. I borrowed most of this from a @Ken-Oscale layout, made a few small adjustments, and added the outer loop. I'm targeting 6x12 because it's about the maximum size for the space I have, and I'll be able to access it from all sides, so while a 3' reach into the center is pushing it, I should be able to handle it. It's also roughly the minimum size we'll need to accommodate an O60 minimum on that outer loop, which will handle the equipment I expect to run the next few years.
With this layout, we get to sit and watch trains run on the outer loops, while the inner "layout" can be used for some switching/operating, too. I have a 4 year old who enjoys the trains, so this should allow us both to operate together. All 3 loops could actually be left independent, sparing the cost of all the switches involved in the crossovers - maybe that is a phased approach to add them in over time. I don't have the outer loops connected here, but there is room to do so as well.
The outer is a compound O67 - there are 3 O60 curves, but everything else is O72+. I'm guessing it might run some O72 equipment, but I won't likely own any for a while...unless I bite the bullet on the Dreyfuss... The middle is compound O57, with a few O48 sections. The inner is O36. Now, if I went with a table width closer to 6'6", we could probably squeeze a true O72 minimum on the outer. I should probably just do that if I'm already so close...
Potential Issues/Discussion Points:
- It's a lot of track. I've never done any real scenery, and since this is somewhat temporary it is not the biggest focus, but I do expect to try some scenery projects on this. There is likely room for a small mountain, or some sort of physical scenery break to hide the trains a bit. Is it too much track? I would like to start adding things like the Menard's buildings for industries, etc. I'm not big on operating accessories these days, but would want to look at adding some signals and other more passive accessories over time.
- I've looked at a ton of track plans, and there are many I'd really like to build, but many of the more interesting ones require substantial elevation changes, scenery, etc. Not sure that I am up for that complexity at this stage. I could see having the outer loop run a grade up/down the back of the layout, with a bridge feature, to add some interest if space allows. So I'm a little concerned about it being flat/boring, especially since I would like elevation changes in an ideal layout, but I think between my current skills and the size, any real elevation over/under type stuff probably won't work here.
- The outer loops could just be double track straight along the top, too. I added the curves for some interest, but there is room to play around with that or even add additional spurs off the middle loop, but too much track may already be an issue.
- The inner loop doesn't NEED that passing siding, but it would allow a train to be stored there while another operates the inner or does some switching. Taking it out creates more room to adjust the main lines, or perhaps add some scenery (mountain/tunnel) at the top of the layout.
- Other concern is just - is this the best use of this space? Can I do better? I've been looking at layouts on the forum for weeks...this is what I decided to put together after reviewing a lot of (great) content.
As always - appreciate the feedback!
