So first off, love the idea.
I think its creative to add bulldozers as a variety of the Armed Guards, but there's so much more you could do.
For example, instead you could add them as a seperate entity (obviously making them more expensive because of the health bonus) and add types of bulldozers besides the black Dozer.
So things like, making Green dozers, black dozers and skull dozers.

Skull being the most expensive with the most health and green being cheapest (Although they'll still be a challenge for the inmates to overpower)

Second, why just stop at bulldozers?
You can easily make tazers (which would be cheaper than guards with tazers), shields (they can only be damaged when attacked by multiple prisoners) and cloakers (Expensive as hell, patrol your prison and instantly KO prisoners).

Aside from these suggestions, its a solid mod as is.
Keep on heisting