windows
By all means a "champagne problem", but half of the time I try to operate roll-up blinds, I get the blinds moving in the wrong direction. The cord is completely outside of the blinds, and it can easily twist, so I can't tell which of the two sides at the bight of the cord to pull.
What mechanisms for opening and closing blinds eliminate this guesswork?
Those 27 inch blinds you link to are top mount and will fit in a 27.5 inch opening without modification. But there are also side mount ones that would also work but you would need to add a 1/4 inch shim to both sides or a 1/2 inch shim to one side.
Most blinds can't be simply cut down in width except those that are designed to be cut to length.
The usual approach is a "crank-type" casement window with a loop in place of the crank handle, and a hook on a pole (try "clerestory pole crank" as a search term) that engages the loop. There are also hex-type versions that use a flexible shaft inside the pole. Or, these days, motors. I'd suggest the hook on a pole, I view motors in this sort of application as things likely to fail and then make the motorized windows useless as they will probably be hard to replace when they fail. Or they'll leave you with inoperable windows during a power outage.... But it is an option.
A hook or hex style operator pole (image from BlaineWindow.com):
I can't make out how the current windows are operated - they might be able to be retrofitted with operators of that type, rather than replacing the whole window, if the only reason for replacing them would be to make them operable from below.
The style that @TDHofstetter mentions, with a catch that's operable by a hook (image from calaifornia-classics.com):
Best Answer
I'm happy with this solution, which separates the up and down runs.