I have dabbled in that kind of stuff. If you wanted a true brush hog type set up with swing blades and a stump jumper, You will have a bunch of money tied up in parts, or a lot of time fabbing them yourself. A modified mower deck probably wont get you the blade to deck clearance needed to cut the tall stuff. I would go with the heaviest blades you can find. The cheap MTD stuff will bend and twist too easy on saplings. I would recommend an electric clutch with an easily accessible on/off switch also.
Thanks for the reply. I'm new to the world of brush hogs, the parts, and the lingo so I've already learned something (stump jumpers). I have more to learn...
As you have pointed out, I'm trying to weigh what it would take and cost to "create my own" versus buy something ready to go or needs minimal adapting. I'm also trying to decide which is the better approach:
1. Adapt a towable brush hog to a 3 point hitch
There are lots of modern units out there, as well as older units like the Bush Hog GT48 or Honda RM-752A. The examples I've found are $500+ for used, and $1000+ for new.
2. Adapt an engine to a 3 pt, PTO driven brush hog
Typically, these are Cat. 1 hitches so the hitch, spindle, and motor would all need to be adapted. The 48" units I have found are about $500.
I have no experience with the towable units (made to go behind an ATV or tractor with no PTO) so I'm not sure how robust they are or if they have stump jumper features. Many seem to have a control box that comes up to the operator for starting (if electric start), throttle, and killing the engine. I have considered a walk-behind brush hog since I could get into more places but I continually read how dangerous they are and if you encounter a stand of multiple saplings of sufficient diameter, it drives up them (rather than through them) as you wrestle with the machine. That doesn't sound like fun.
What would be the minimum engine size for a project like this? It seems that the heavier duty Swisher mowers are 14-15HP. That Bush Hog I found has a 13HP Honda so it seems that 13-15HP is the usable range.