Okay Since we got retainers and we can place them under a combat class which we already have leveled up heres a small idea

We create a 1 player dutys using the retainer of our choice to back us for rewards

dungons could award extra gil or special items how this would work is simple
we que up when we put the que up we select are retainer and we fight along side of our retainers issueing them commands and so forwth using the classic system of ffs that go by turn base

as for pvp it would work like this
this would 1 verse 1 but using the retainers its more like 2 v 2 again using a turn base system

there really isnt any reason why we cant do this we got the retainers we got a que system and we can give the retainers equipment