Not sure of the type of work you are doing, so my ideas may not apply, but they might get you thinking of some ideas that would work.
First a 4Tb portable external drive, USB 3 or thunderbolt is pretty small 2 drive stripe 0 arrays and performs pretty well (150-190 MB/s). You could use carbon copy cloner or similar utility to sync over the workstation version of your catalog and files to take on the road, then sync it back when you return. Pretty simple method. Obviously at some point 4TB's might not be enough, so maybe not a real workable solution, unless you cull the older stuff to keep the size manageable.
Following your "checked out" collection idea, you could export that collection as a catalog to use on the laptop. You can import new files and work on files while on the road, then import that catalog back in to the workstation catalog, which should overwrite any changes and add they new stuff.
My current workflow keeps all my new images and recent working files on a 600gb partition on my laptop SSD. When I work on them, I use target disk mode and plug the laptop in as a hard drive. A backup program (carbon copy cloner) triggers a backup as soon as it sees the laptop hard drive, but when I go to work I'm working on the laptop drive itself. Very fast (thunderbolt connection with an SSD, Black Magic write test at over 700 MB/s). Basically I only have one work drive, and theoretically could plug it into any computer that has Lr on it. When I'm finished and don't need them on the laptop, I drag them to another folder that's on my workstation, so they are not longer editable on the road, although I can still view them.