I hope that does not sound rude now but:
I recommand reading the long post I had answered you above. If this is not enough help I do not know what to do else, as we are not going to create your addon for you
As I had written above: Group management is nothing you should start with if you want to create your first addon! You should first create something easy with your own UI and understand how that works and how data from lua will be send to the XML created controls.
The eso code shows you that they just use 1 XML template where they can add several new controls (1 per character in the group) dynamically.
And you should do the similar there, or you will get intro trouble if you "hardcode up to 12 or 24 group frames manually".
So your goal should be to understand how the vanilla ESO code works and does that, so you are able to create smething similar for your addon.
This is just my understanding, off course you can go ahead and create 12-24 harcoded XML structures for each player and update them each time redundantly, if you like to.