Yes, it would only be for short distances.
I would like to get some sort of technique for pressing the outer hull in a single piece, or maybe two pieces and then pressing/riveting them together, but I am not sure that we are ready for all-metal hulls...
Ooooh, I think that I forgot to mention that it is meant to have 6 'crew' and 12 'soldiers' with a lot of mixing of duties. It is mostly designed to travel in packs and utilise boarding manoeuvres. Ramming is one of the things that I would be tempted to forgo, it is a lot of weight and damages the victim while tending to get you stuck to them. Great for building a secure platform to board from, but not so good for sailing your prize away. The cannons are largely suppression with carcass or canister shot and for attacking in packs while the torpedoes would be primarily to thin out the numbers of a force with superior tonnage. They are only about 35 feet long so not big. I would be tempted to try to get them smaller but that would eat into their length to width ratio...
Really, there is a lot wrong with the idea, but It is the ship that we can get now, with a lot of innovations that are best for short-range vessels and not so useful for stealing for a major warship... I would rather desing some grand flagship that can rend the seas, but that would be inappropriate without a shiny new cannon to equip it with...
If someone wishes to add an updated Grommell class than that would be just grand!
P.S.
Adding metal hull and crew compliment to Grommell Proposal.
And I forgot to mention that it has a normal rudder...
P.P.S.
I would never expect a Grommell to serve effectively in two engagements without resupplying at the least. They could someday be supplied by some sort of supply barge and maybe even carried or towed or something for longer missions, but not really intended for anything other than skirmishes. Ideally they capture prizes that can battle in the open.
Oh, and I say that it has two decks, but there is basically nothing underneath the lower deck, it is just a platform to stand on and stabilise the structure a little.
P.P.P.S.
Maybe it needs some sort of wedge to spread out the air jets and get more 'grip'. Or perhaps water jets... Ehh, I have already done too much...