...does seem to need a special rivet gun (of course Iím always open to a new tool)...
My manual rivet nut insertion tool works like a regular blind rivet puller, but instead of jaws to grip the rivet mandrel it has a threaded stud to go into the nut. It looks like this one: Wicks - RIVNUT TOOL 8-32, 10-24, 10-32
. As with rivets, there are a selection of nosepieces with different screw sizes which interchange on the same tool. Compared to power tools, this is a cheap device, which could possibly be justified by a single use if it did just what's needed.
Aircraft Spruce and Specialty - Tools - Rivnut Tools
and the Wicks page
shows some strange tools for this purpose. I think the weird wedge-based tool at the top of the Aircraft Spruce page is about the price I paid for my squeeze-handle style tool (approx $20 Cdn, or maybe more, but it came with a bunch of nuts).
Today I found this interesting link: Pulling Rivnuts without a Rivnut Tool
I have not tried this, but at a quick glance it makes sense to me.
...Lastly, they tend to be fairly large bolt sizes.
I don't know what other people consider "fairly large bolt sizes", but my tool has sizes including #8, #10, and 1/4" (and one or two more). I find that the smaller thread sizes don't have enough threads in the nut to work well in aluminum: that is, it is too easy to strip the rivet nut threads by squeezing the tool just a bit too hard when setting the rivet nut. I have even had this problem with the 1/4" size, but the solution in some cases is just to use steel instead of aluminum.
The large required hole size is a problem with almost any hollow-wall fastener, as the hole needs to clear the fastener thread plus some more working space for the rest of the hardware - in this case, the nut thread plus the surrounding wall of the nut body.
I have only installed one item in the Boler
with these fasteners; I bought it for an automotive job.