Hi friends,
Waooo, plasma or waterjet, that's not the common tool everyone has in his shop :-)

But, it's true that it's difficult to answer such a question without knowing what is in the shop and what's the skill of the builder ...
and it depends if it's just for making one or a full equipment for a company of firemen ...

My just two cent idea, assuming at the opposite that it could be a single tool, on the low tech side, I would just say that a reasonably thick steel plate can be cut with a jigsaw with HSS or bi-metal blades (probably several), and a lot of patience.
I would add some elbow grease, for the filing after that in order to clean up the cut.
Some oil to lubricate the cut can help also.

For attaching the handle, you will probably need to weld a piece a steel pipe.
Please give us your feedback !
Christophe