My rule with HF tools, especially powered tools is that if I needed it for just one job and there was no other way to get the tool (rent or borrow) and there was no other way to do the job, the cost of the HF tool paid for itself on the one and only job. After that job, all other uses are "free" and the tool gods will keep that tool working for a very long time.

My situation with a HF roto hammer came after using a borrowed one for a bunch of tasks and then I didn't have access to it any more. So, I bought one and years later, I have put anchor holes of all sizes. At the time, I didn't think I had much more use, but the opportunities to use the tool come up over and over.

I can't say the sheet metal application would work or not, but I have used a chisel to wedge a cut open so I could finish the cut, used a chisel to peel a weld apart. used a tapered pin to slightly enlarge a hole when trying to slightly enlarge a hole was too hard to hold the drill which grabs before breaking through, used a pin punch to drive a really rusty bolt out of a hole...

When doing those kind of things, hearing protection is a must...