I think you’ve identified the three broad use cases, and three different markets: that of the non-ham Wifi antenna tweaker, the ham antenna tweaker, and the RF circuit builder.
I would think it would be reasonable that your average ham antenna tweaker would also want to go down to 3.5 if not 1.8MHz though.
I have an old Anritsu Sitemaster VNA that’s single port but because it’s battery powered and handheld, it’s very useful for antenna tuning and setup outside in he field, coverage is 25MHz to 3GHz.
On the bench I have an HP 8753A, 300kHz to 3GHz, which, with an accompanying TR test set, will do two port as well as one port measurements. For practical antenna measurements, except for small aperture microwave antennas it’s less than ideal because it’s hardly portable!
In my experience, don’t underestimate the size of the ham market. If you have a unique product at a reasonable price, they will come, but without HF capability it will rather limit that market. Word of mouth is strong. The non-ham market is undoubtedly much smaller. You need to make sure you extol the key differentiators between your product and any competitors, as there are already products like miniVNA and PocketVNA out there which will fragment your market.