Agreed, ohhhh that would be soo awesome to see him witness battle.
Yes, Theon will have to claim Pyke via force. There are a lot of options such as, Stannis wins and Theon finishes him with Manderly fleet (not likely but this chapter was more than unlikely to predict), Ironborn betray Euron, they get crushed by Redwynes or maybe even Hightowers,...
I dont know who will rule at the end but Euron will fall eventually.
I just dont see Theon winning Kingsmoot even if Euron would ever accept one. After 3 minutes of taunting he would start to call himself Reek and Ironborn dont want Reek as a King.