I hate to say it but I think the Hi-Z option could well be an optional extra in a separate box, because IMHO ordinary Hi-Zs are just not high enough most of the time. Likewise ordinary DI boxes. I really did mean megohms when I said it. 220K is not going to cut it.

Anyway the ultra-Hi-Z inputs would want to be jack, which would bugger up the Cannon-ins, and the combined XLR/Jack is just another thing to go wrong.

You were right first time (apart from circuit-board mounted sockets and controls) - if it's a mic preamp, make it a dedicated one. Flexibility is the mother of abortion.....

What would be neat as an extra would be a mini-DI-box, jack in XLR out taking its power off the phantom. Then I imagine you could have a switchable impedance, about 33k for people with preamps in their guitars, 3.3meg for those without