It sounds like you have a solid idea of what it will take.
Personally, I think one day a week is too little for the average horse (that is, non-retired, adult horse), but I am also under the impression that many people spend less time with their horses than I traditionally have.
Can I ask why you're considering another horse? Will it fulfill some role that you current horse does not? Or are you wanting a second one for some other reason?
The sensitivity of the internet baffles me.