I have a similiar sized machine- 19 PTO HP- I am shopping for a rough cut mower as well and would not consider larger than 54" and then only for light material- the issue with RC mowers is not the amount that they are cutting but the weight of the cutting blade as they don't cut as much as they smash materials using the weight of the blade- the weight of larger RC mowers can really strain the PTO system at engagement because of the inertia needed to get a heavier blade started moving. Also, you need to decide between shear pin and clutch- if not using frequently the clutch can rust together and actually not offer any protection- you need to "break" apart the clutch faces everytime you use it unless it is used regularly.
If I were building a log splitter I would look for a pto driven pump- the GPM flow is going to pretty slow on that machine I think.
Make sure you get a cat 0 PHD- the height of the machine is often a limiting factor. i'm surprised that machine can handle a 72" blade as a 60" pushes my machine around with a heavy load.
ExMark Commercial 30
Stihl FS250- Grass blade
Stihl FS110R- Edger/135* Bar Hedge trimmer
Stihl FS110R- string
Stihl 290 Farm Boss 20" bar
Poulan Pro 16" bar
Poulan Pro 18" Bar
Stihl HT101 Pole Saw
2004 Massey Ferguson GC2300- 2350 Loader w/ toothbar, 60" Kioti Aerator, 48" dethatcher, 60" back blade, 48" box blade, 3PTH pallet forks/carry all, 48" lawn roller