The problem:
Lantana creates lumps of bushes 2 -3 meter tall.
I could not find reasonable tool/ device to attack those dense but lightweight bushes on my property.

Hend held trimmers are too small to clear acreage, but crawlers machinery too expensive to consider.
Nothing in the middle.
Solution: I am looking for is something like a self-propelled mower that could chew on light bushes in the front.

Did anybody come across device or tool/attachment to destroy bushes, at a reasonably low price?

I am now thinking about building myself machine - sort of typical mower but in a vertical position that I could push into bushes to mulch it to pieces.
The options are:
1) Typical mower blades - round disk with short swinging blades
2) flail drum with hammers

Australia is still full of bushes to clear ( and lantana is an awful pest).
Can somebody help here?