Gary, please don't think I am being pedantic. It looks like a really great idea to me, there are just some details I cannot quite visualise.
1. I get the rationale for the threaded rods, but what if one or two are turned a bit more or a bit less than the others? Will that not affect h angle of the planer sole and blades? I get that even though the planer is “dropped in”, it is being held down by the operator’s hand, but if the box is out of level, the cut will be out of level - I would not be able to correct by feel.
2. Assuming the depth of cut is set only via the threaded rods, should the planer’s own depth of cut be set to 0.1, 0,5, 1, or 2,5mm? I realise that all the planer’s depth adjustment does, is raise or lower the forward section of the soleplate, but since that movement exposes more or less of the cutters, I assume the initial setting will be of some importance? Perhaps it needs to be determined by trial and error.