A round baler like you want would need about 45 pto hp, something like the JD 448 baler or similar. There are lotsa tractors in this hp range. For example, my haying tractor is a 2008 Mahindra 5525 (54 hp engine, 45 hp pto, 2WD, partial constant mesh tranny, power steering).
I traded that little 21 hp (engine ) 2005 Kubota B7510HST in the photo for the 5525 last year.
My old 1964 MF 135 diesel is a field tractor that's been modified for orchard work by using short front axle spindles and replacing the 28" rear wheel rims with 16" dia rims.
The 135 rear axle is 20" above grade and the tires are 83" wide (measured to the outside tire wall). The 5525 has standard 28" dia rims so the rear axle is 25" above grade with tire width of 71" with the rear wheels adjusted for max track width.
If stability is a major concern of yours, you could lower your tractor's CG similar to the way it was done with my MF-135. Or you might be able to use dual rear wheels to widen the track and take the tippiness out of your ride.