I am sort of in the same category. I'd like to do some farming, but the 20something PTO hp on the lightweight CUT just wont cut it. It has sort of fallen short in several areas over the years, but its what we have and all the current attachments are sized for it. Were I shopping for a new tractor, I'd say at least 50hp, but since There is what there already, a larger replacement tractor and re-upping all the attachments we use all the time would never pay for itself.
I have been giving some thought to turning 4x4 pickup into a tractor. I figure I could do some sort of slide-in that might lock into the trailer hitch with a dedicated engine for PTO and maybe hydraulics. I could probably get a big old used tractor for less (just a 38hp Kohler goes for about $2500), but I am thinking about it.