"For a "new" amiga-like OS, what parts are important for you?"
Any and all. Let the end user decide. I love building my own machines at home (although they are all PC's). Don't restrict it to one (or a few) types of hardware like Apple does.
"What sort of hardware should it support?"
Any and all.
"What sort of hardware can you go without?"
Let the user decide.
"What features should be present?"
Speed! I want a very fast OS, not bloatware like Windows. Let me decide on what options to install.
"What are "must have's" from the old amiga os?"
It should (or must) run the old Amiga software from the 80's and 90's even if it runs it in a virtualized manner.
"In short, what is your wishlist?"
A very fast, open source, freely distributable OS that can be loaded on any type of hardware (x86, PPC, ARM, etc...). It should have the look and feel of the old Amiga OS's but up to date. It should support the latest hardware and software but also be able to run the old Amiga software (virtualized most likely).
That would be paradise for me.