I've only been able to play a limited number of PvP matches, but there's a couple of things I've sort of mulled over:
I feel the power ups need further limitation, either a time limit (30sec-60sec) to stop someone becoming a hoarder powerhouse or a quantity limit; 3-4 max until you're sunk. Whilst fun to sit in the back and collect, emerge to blitz then slink back probably better to only reward that for a short period of time.
For some of the longer matches, "capture the flag" esque maps I worry about the power imbalance for late joiners. One match I joined some had the 900 silver ship and upwards, absolutely outclassing the little starter ship. I know it's not uncommon to join a losing battle in games, just needs like a little silver coin join bonus after 5mins as not to feel like a fish in a barrel.
Last is more a suggestion I heard from Parrot which I think was an awesome idea, a PvP match which is more King of the Hill/Ocean type map. More ships in the middle, more points gained but the other team will have a chance to grab the powerups(?)
That's my two cents on that, but overall it's been a blast in the PvP arenas!