I see what you mean! And you are right! But perhaps it could be omitted if it wasn't a group chat and added left of the bubble (outside) with a light grey since the bubble has horizontal size limits (I might be mistaken). The top bar would then proceed to display the Group chat image, the status mini icon would disappear and by pressing the bar (just like in standard messaging) it would open a list with all the participants as well as when they were last seen/online (and the mini availability icons could be there as well). I can do a mock up of a group chat if you want.

As for the yellow icon, it could have a checkmark but I think it's more logical (even if it goes against Whatsapp itself) to have it as a pending icon because it's only really "ready" when the other person has the text on their device!