A better way to route shallow recesses

[Dark Mavis]

So, I like so set things like control plates, pickup rings (the flat kind), switch plates, etc into recesses the same depth as the part, and a little larger in footprint so it gives the appearance of a quare sided trench around the part. It looks kinda cool. BUT it's a pain to do. I have an 8mm router and finding bits for it is a pain. Template cutters don't have a small enough radius for the corners quite often, so I have to use an 8mm cutter and use the shank against the template. But because of how shallow the recess is, I need to make a template, then attach the template to a thick piece of wood and route that out too to make an extra thick template to give me the stand-off I need to make such a shallow route while still keeping the shank against the template. It's a total pain.

 I don't wanna make a thin top separately and cut out the recesses. Though...if I were going to paint the guitar a solid colour I totally would. I'm thinking of taking a normal straight 8mm cutter and somehow cutting it down in height, but I have a feeling those carbide blades are just glued in and would probably break free and fly away during the operation. I know a pin router would solve all this, but I make like one guitar every couple of years, or whenever I feel like it. I don't do it as a business and can't justify the expense.

 Any ideas? I make the initial template out of hardboard and reinforce the edge with soome CA. I actually use the router too route the template, and use teeny sanding blocks to finish it up nice and neat. Then attach it to a couple of old pine shelves or something for thickness. It's just a really inefficient process. I can't just use some scrap wood to raise the template, cus I need the bottom of the template to be accurate too so I can get it in exactly the right place. I can't do that if the template is up an inch or two off the guitar. Maybe I can make the first hardboard template, then use some blocks as spacers and attach a second piece of hardboard as the "bottom" part of the template, and then use the router to match the bottom template to the top template...

 Is there such thing as an 8mm shank straight cutter with 8mm cutter diameter without the unneccessarily big gap between the shank and where the cutters begin, and which has a depth of not more than say 5mm?

If the router had a round base, I could make an oversized template to use the router base as a guide, but it's not round. I guess making a round base is an option but then I suddenly have to make huge templates and figure out how to extend the template design out by the right amount to compensate for the size of the router base.

 I'd try cutting down an 8mm drill bit, but I don't think that would leave the bottom of the route in a very tidy state.and I'm sure the speed of a router would overheat any drill bit pretty quickly.

Every site I've looked on has an extremely limited selection of 8mm cutters, but surely something as simple as routing a shallow recess using a template shouldn't require all this MacGuyvering...

A cutter like the one in the picture, would be perfect