Got a question.. am i right in thinking this handle could be rotated to pull front/back? Might be slightly more intuitive that way if used for the top link. I can't tell from the pic if it would interfere with the next handle's silver 'body' or not.
Hydraulic top link.. yes! Once you have used a power top link with a box blade you'll never want to touch a box blade without a power top link. Like if i told someone i used my box blade for this or that and they said "can you get on my tractor and show me what you're talking about" and they didn't have a power top link, id be like.. ehhhh.. let's change the subject lol.
I used an electric-over-hydraulic cylinder for mine on my small Kubota B6100. I bought two of them with the thought i'd put the other one on my Case but have not done so yet. Obviously real hydraulics is the way to go if you've got the valves and plumbing all planned out. I have thought about a 'tilt' link but haven't talked myself into it yet. Seems like a lot of hassle for something i wouldn't use that often, plus it would practically have to have a load holding valve or inline cutoff to keep from 'drifting' all the time. What i HAVE spent a lot of time thinking about, is modifying my next angle blade for tilt, manually. I don't have as much desire to tilt my box blade.
As far as the 3pt mower, I like the idea but i think a 'conventional' 3pt mower won't get you as far under a tree as you might like. If you extend it far enough rearward your tractor, with no loader, would need a ton of front counterweight. Going back to my b6100 (only a bit bigger than Case) with an FEL, 4' bush hog is no problem. On a b7100 i have (same basic tractor) with no loader, same bush hog plus 3x55lb weights up front, still does not have a lot of steering authority.
What i think might be a better idea in your case, since it would be hydraulically driven, is to front mount this mower. Maybe make it able to use the same lift mechanism you'll be building for your plow. The tractor is already heavier at the rear, plus the 3pt can pick up another 500+lbs, plus your head is further from that end of the tractor. If you draw a line from the top of the mower deck to the top of your head with the 3pt design, it really only gets you 3-4ft further under a tree before hitting your head on branches, than a mid mount mower! Draw the same line in the front and it's more like a 5-6ft difference, plus you could make the thing 'extendable' if you wanted. Something like a 2.5" square tube nested inside a 3" square tube, with a couple of crosspin holes, could make it extend by several feet pretty easily. If it extends AND angles up far enough on the lift mechanism, would also make it pretty easy to do blade repair/maintenance. And heck, you could still put 3pt brackets on it and use it that way too. Or maybe this is just too much scope creep. 😂
So as much as i like an elegant implementation, i think you might be overthinking fan control. I would venture that you would be totally fine with on/off. Let the actual thermostat do the 'metering' and have the fan just be on/off. The only thing that i would say is too simple of a switching circuit will have it click on and off repeatedly when near the set point. Something that actually turns it on and off at different temps would be better in that sense.
As far as the hydraulic cooling, I have NO fan on my Predator 212-repowered Case 444, and i have not 'overheated' the hydraulics. However, it is purely a push/pull machine and i don't do any PTO anything with it.
Is there any room between the front of the hydraulic cooler and the grille?