Hmm, well thanks for those thoughts. I'm not sure I want to do loose tenons though; I don't like the idea of trying to put the mortises into the ends of the long bed rails. Not quite sure how I'd do that. A more traditional tenon would be easier for me.
As for the router jig, I found a couple ideas but not quite 100% what I'm looking for.
This Rockler centering jig looks like it would do the job. You can't take it all the way to the edge of the rail, but perhaps it would get close enough. It also doesn't look like it would help with tipping, and if you rotate the router during the cut at all, then you loose your straight tenon walls. https://www.rockler.com/mortise-centering-router-base
I could just use the router fence, but again that leaves the human element to consider.
This Woodsmith plan looks closer, but centering it is still manual. I'm concerned about changing orientations between the left and right side (for example) and having them be off. Or referencing different faces between the upper and lower rails on the headboard. https://www.woodsmith.com/article/router-jig-for-perfect-mortises/
This one is self-centering, but again, DIY and I don't really trust myself to make it within tolerance. Also it would be nice to just buy something (as long as it's not super expensive). I don't get nearly enough shop time as it is.
This last idea is what I'm looking for, but pre-fab plug and play. Is anyone aware if somebody makes something like this?
