The reason I put it in there in the first place, is that if Metal gets separated from his Guitar, he is at least able to hold his own at a PL10 level. When you bring in the Flight and Speed/Quickness arrays, that gives him mobility, and an ability to invent at a very respectable speed.
...also, he's a cyborg. He should be able to hit someone respectably hard.
As for saving 10pp for future use, that's not how Invention works. To invent things, you need to spend time and make skill rolls. You can't spend PP on the fly as a regular thing, unless you want to do something like:
Gadgets (Variable Power 2, Easily Removable) [10pp]
Which would let you spend 10pp on powers and reconfigure.