Such great input @ciane and @Sandraelle , I'm loving it! OK I did play around with the 4-wide, however am also in favour of routing vs realistic.
Using a 15-wide lot, the largest only goes up to 20 which restricts the length of the cars to 16. You’ll be losing some space at both ends for the doors and front insets (see screenshot), so basically with a 6-wide you'll have a rectangular 10 x 6 plus the odd space to put the all-in-ones and ad hoc items (see screenshot). Would that be enough space for your needs? 5-wide would reduce it even further.
If that is too little space for your needs, I would keep the engine on a 20 x 30 since it also houses the coal car and is basically almost done, however can go down to a 20 x 25 lot for the cars. If my math is correct, you would have a rectangular 6 x 15 area to work with plus the odd space top and bottom. While I should be able to tweak the CFE for a 5-wide, I'm thinking since we have the additional space anyway, why not utilize it.
Soo... your thoughts... 6 wide on a 20 x 15 or 20 x 25?
https://i.imgur.com/df4SIlX.jpg