Ah, yes, there's no plan to add support for the kind of cutting geometry that router bits entail specifically because PixelCNC's toolpathing and CNC simulation engine - and the core systems they're built on - operate on the assumption that for each XY point on a project or cutter there is a single corresponding Z coordinate, as opposed to multiple Z coordinates.
PixelCNC has always been intended for 3-axis milling/carving the "top" of a project - where cuts are entered/exited vertically, as opposed to entering and routing along edges from a sideways approach. However, I might be able to at least add some kind of support for another cut entry method - which would allow a toolpath to approach a cut from a distance away and move inward to the cut along a fixed Z, as well as retract at a fixed Z a specified distance before rapiding to the safe Z level. Then you could just define a generic endmill to generate the path with. I can't promise this will even be a thing as I already have plenty on my plate and hope to get to beta before summer but I'll keep it in mind :)