This is late, but I would have many different gauges of wire and many different types of connectors. I’m just an individual making things in my motorhome and I always seem to have to pause a project to order the right connector.
USB cables to connect to computers for programming.
And, of course, a few computers with nice monitors for both using the CAD programs and analyzing data from the robots.
A good internal WiFi network.
I agree about a couple good soldering stations. You might also want a hot-air rework station. I would suggest that you do not get cheap stations. It may seem wasteful to spend hundreds of dollars on a soldering station, but I’ve never regretted it.
Magnetic mats or boxes with many compartments for storing screws that you take out of devices and want to put back without losing any.
Standoffs so that you can install boards onto your robots.