Increased performance would use more battery life to, well, increase performance. My HP PC has an option for this. But to add the increase performance feature, they would probably have to lower the default performance a little. Which would mean that the overall system would need to be faster. Probably a feature for newer devices only.
Not exactly needed on a mobile device. The software requests the 'higher performance' when needed and turns it off when it no longer is. I can understand the low power mode (my only complaint is why they didn't put in an earlier release of iOS) but not increase performance.
Also, I vote to keep the compass app separate. I use the level quite often and it works pretty well in a pinch or to settle a bet.
Otherwise, I pretty much agree with everything else you listed. Oh, and FYI, the extensions hosting is for OS X, not iOS. iOS is only supporting ad blockers now, not full on plugins TMK.