OK. Maybe gotta rethink this whole deal.
We got a router and not a whole bunch of money or much of anything else in the line of wordworking stuff, right?
Chances are this a one shot deal or at least only an occasional thing, at least for now, so a whole lot of capital expenditure is not warranted.
Able to compromise quality to some degree. (not so they look like they been chopped out with an axe but also don't need to look like the been run on a laser cutter either).
If you can settle for dovetails instead of box joints, take a look at this link: The EZ Pro Dovetail Jig Makes Perfect Through Joints & Dovetail Joints! - General Tools & Instruments
Click on the "Instructions/FAQ" link for a video.
For $60 (free shipping on orders over $50) it comes with everything except wood, router and vice to make 1/2" Dovetails.
I don't see why it can't make box joints either with a guide bushing and straight bit but I don't know for sure yet. I just ordered one last week and it isn't here yet.
Advantages to you, as I see it.
No maximum width of stock, just need to run them in 6" sections, reindexing each section.
Can be run either on a table or handheld.
Cost about the same as a high end router plate, not to mention table top, template, etc.
My Dad used to tell me "If you can't get what you expect, change your expectations"