The CK 35 should handle a 6' finish mower easy, and would probably run a 7'.
I run a 7' rear discharge rear finish mower on my DK 35 and it handles the mower, no problem.
If I went the RFM route, it would be 6ft minimum, maybe 7. The Kioti would have no problem with either. My land is not wide open. Some parts are an obstacle course, there are some open areas, around the house there are a lot of flower beds that curve in and out (the previous owner was a gardening nut, I've pulled out half the beds, else I'd need a fulltime gardener). The reason I don't want to go that way is because I bought the tractor to be tractor, maximum traction, heavy, etc. Most of the time it would kill the lawn. The other reason is maneuverability. While the RFM would be better than the H's mid mower, I think I still would have to have something smaller to get in a couple real tight spots. An example is in back of the house, where the mower has to deal with the contours of the flower bed, the patio, the birdfeeder, well pump head, birch stump, and two small trees. While there is plenty of clearance for a 60" or 72" deck, even without the loader, it would be a real pain to get the tractor in there.
The best option actually would be a SCUT with MMM and loader, that could get in tight areas and do landscape work on the lawn without bringing in the Kioti. But I'm not spending the 18K for another tractor. The same applies for the front mowers. While they might be useful, I'm afraid they are out of the budget. A zero turn will work just fine there, no need to pay 5K more.
I'll sit down and go over specs this weekend, look at brands online, see what's out there. I have time on this, and I plan to use it.