The danger with power creep is that luck of the draw becomes the dominant determinant of who wins games, not player skill and decisions.
For example, PikaRom can attach on T1 (going second) with a lucky draw (attach + koko prism for an energy onto the bench + thunder mountain + jirachi escapes/switches out) - and his raw power wins games before the opponent can set up. Even if PikaRom sets up on turn two, that's still game winning power with minimal thought and all based on draw.
This ruins the game since matches are better when they go back and forth and require both players to make decisions that decide the match.
The Tag Team mechanic is already infusing a little power creep. I don't think amplifying the mechanic is a wise idea. Too often, PTCG underestimates the Meta and players find ways to combine the cards that they didn't see/intend. That's the thing about power creep - it won't be the first set of cards that does it, it will be the second or third set when the combinations come together. Here's how you will know when we crossed the tipping point: 50% of matches get determined by luck of the draw in the first two turns. (this killed MTG)