No changes in progressing units from G12 to 13?

They're encouraging a Grow Tall vision of roster development, and bringing fewer toons to relics but giving them more relic tiers once they get there is consistent with that. 

You may simply need to leave your older toons at g12 for longer than you thought to make sure you have g12 pieces for new toons. 

But in any case, having more choices for your Mk2 spending doesn't make g12 pieces harder to come by. Only you get to choose how you spend that Mk2 currency.