I have no experience with hydraulics so I cant help you on that side but from my experience of current armour technology, it wouldnt work. The majority of bots are armoured in hardox, titanium or layers and layers of various plastics etc. Trying to pierce through is exceptionally tough.

You are also relying on a number of events to take place for the weapon to work. This rarely happens in the arena.

Look at the series 1 and 2 machines that had bits that drew opponents in and then did various things to them. They never worked as the most effective weapons are the ones that rely on a single action. flip, smack, crush etc.