What a terrible precedent it sets.  Become a team captain, be a team leader in receptions, get mad because you are not targeted more, go public with your complaints (through your dad), and then make plans to play for your team's rival.  Then, when your leaving did not hurt your team as you thought (or perhaps hoped), you ask to return.  

I just think the bridge is burned.  If the coaches allowed this, I just think it would be terrible - especially for those guys who have stepped up at TE since his departure.  Both sides just need to move on.  That doesn't mean the coaches and former teammates have to hate on him, it is just not good to allow that kind of person to be on the team IMO.

Now, having said that, if there are some extenuating circumstances that changes hearts with the coaches and players (maybe he was under duress/stress or there is some other situation we know nothing about), I would defer to them.