There is already some discussion ongoing in the Whonix-Live mode thread but I guess a dedicated thread is more suitable.
What would you consider important for an (official) Whonix host OS?
Which OS should be used?
Similar to @Hexagon I would also suggest something debian based. Linux Mint is said to be the most user friendly for linux newbies but as far as I know the security track is not good.
However, Debian is usually not that up to date so it might not run on the latest and greatest hardware. Maybe using backports and tracking the vanilla kernel could help to some extend.
I think Fedora is more up to date but hence it also is more volatile and changes happen more often. Practically I don't have much experiences with it.
There is already qubes-whonix and I would like to use Qubes but (in particular with the upcoming 4.0 version) hardware support will be even more of a problem.
UEFI and graphics drivers are the biggest issues I can think of and then maybe other drivers for ethernet, wifi ... .
Tails and Knoppix work on most hardware I have so installing the same packages would probably solve most problems with drivers
Most stuff should happen in VMs.
For general usability maybe network manager and a browser for captive portals would be useful. This could maybe also be implemented in a VM; starts to look like Qubes then ...
Full disk encryption should be mandatory. For this you either need an installer/tutorial or make an already encrypted image available with some setup utility where the user changes the master key and password, expands the image to fill the disk ...
In general I think a hd image which is just transferred to an USB stick or normal hard drive would be the most useful. The advantage for the end user would be a rather easy setup (except maybe FDE) and using a host which does not spy on the user.
Disadvantages would be the need to download a likely big image, customization will be harder (not a disadvantage regarding anonymity), driver problems (but could be the same if you install manually), a higher workload for the devs.