PIC18 USB Programmer

[r0nd0m]

Hi there ppl.

Im here wondering if could I design my own PIC18 usb programmer. I chose this PIC cause it already has the usb hardware on it so its gonna be easier to assembly the parts.

But as Im kinda noob, I want you guys to tell if am I wrong or not on this:

If Im gonna create a new programmer board from scratch but I dont wanna create a software also, I need to make the board compatible to known programming softwares (Icprog, to me). But how can I know if my board will be compatible to the programing software logic? (Or theres no way to create a totally new board, and we can just modificate the existing ones ?)

So my question is: What are the patterns used to create a programmer? Is there a specific "check-list" or I just need to worry about making my hardware to work? (I dunno if you guys could understand me, I meant as following the usb specifications, filtering noises, ending transmission lines correctly, powering correctly, etc..)

Thank you, guys.
Cya!