For really deep cuts, there is no ideal solution. A Z-independent dust shoe helps, but 2.5" is deep enough that even then, dust collection won’t be great, depending on what you cut. If cutting large pockets 2.5" deep, a Z independent dust shoe would still have the bottom of the shoe at the original stock surface…2.5" above the bottom of the pocket, so by the end of the job it’s not sucking much.
Right now a PwnCNC model seems to be your best bet (probably with some adaptation required) if you want to go the “off-the-shelf” way. But since you mentioned designing and 3D-printing your own shoe, you could also design a Z-independent yourself. I’ve been down to (pretty deep) rabbit hole, and if you do have the time it takes to design and print it, it’s quite rewarding. Here’s my take on one that adapts to the HDZ 4.0, that @MarkDGaal helped me rework to accomodate the trim router instead of my bulky spindle:
The one type of dust shoe I did not experiment with yet is the “floating” kind, which may perform better for deep pockets as it can be set to have the bottom of its brushes lower than Z zero:
