keep in mind I only know enough about this stuff to be dangerous.
Switchmode. For people who want huge current draws, why not have one or two outputs that have switch-mode setups ala' the onespot. Just make sure to have all the snubbers and whatnot so the quality of the traditional rectified ac side isn't messed with (and my whole powerline, but I think for CE cert you have to put all that stuff in anyway, unless DIY has some loopholes)
This may have to be a kit that requires to set some options up for people ahead of time; say you have 6 outputs, you can have it so we can decide to have up to 2outputs switchmode and 4 standard transformer, or 6 standard transformers or 1 and 5 etc.
and have options for the transformers side..you can have all of them have the sag option or as few as one. I'm not sure how that's going to work logistically what with all the extra holes.
Panel/internal accsess for the DC voltage switch would be cool, have a little door or something, I have a feeling someone might mess with it out in the open
if you put everything together right, All you'll really have to do is just ship different things, all the boards and enclosures ,ideally, would be the same.
Power is a really personal thing, so I think it should be somewhat custom. You have an advantage over voodoo labs, since a lot of the work is done by the customer, you don't have to make a one size fits all product.
It's a great idea regardless, good luck