If you do wind up getting the Sherline, you could extend the capacity of it by adding a second high speed spindle to the side of the head itself rather than rails. You could make identical mounts for each side of the head. Swap out the spindle to the other side for the second op. That would leave the parts mounted to the table. That would gain you a few extra inches that you might need. Making those mounts could be one of the Sherliine's first jobs.
Now finding a US made high speed spindle might pose a problem. Not all FOREIGN tools are poorly made. Europe, Mexico, Japan, Taiwan, Brazil all produce some good quality tools. Great in some cases. I'm reffering to power tools mainly. Some are US owned, but made elsewhere. Germany produces some of the best power tools made today. Japan used to, but not as much IMO.
This one is designed in Germany, but likely produced in China or Taiwan.
Proxxon 28483 High Speed Rotary Grinder Motor Collet 220volt CNC Spindle Drill | eBay
Still a step above a Dremel IMO.