I appreciate the sentiment, but I'm not completely sold on this one.
There is a personal rating that (I think) factors into match-ups. As such, you shouldn't get a bunch of active caps continually fighting level 40-somethings regardless of team rating. Put another way, there is a reason that my team at 1600 faces cap teams with a rating of 40.
There are other confounding factors. For example, you get cap teams where only one member is active and the others are afk. Their rating stays low because they lose, but arena is important for the farming bonus. It's not manipulation of the ratings, just a way of getting the bonus.
I agree with Jadakris that teams don't play Nod to manipulate arena ratings. Tokens are nice, yes, but I can't think of a season where I didn't end up with lots left over. My suspicion is that this isn't the driver.
TJ commented in a thread about arena playoffs that getting teams together on a regular basis was difficult if they came from different time zones and that scheduled playoffs would be very difficult. I think that what you are seeing is that many teams don't want to put the effort into maintaining a constant team until they need to get serious at the end of the season.
The ideal solution to this would be for Jeff to have a season every two months and so you couldn't afford to take time off/rearrange your team. I don't think that's going to happen... although we can ask.
Perhaps the solution is to reward teams that stick together (e.g. a rating bonus based on overall time queued). This would discourage the behaviour you describe by handicapping teams that focus only on that last rush to the finish.