Best way to combine for an inverter to use and charge 2 different battery technologies

[Roadrunner0]

I have a 48vdc 24kw L16 battery bank and I want to add a 48vdc 20kw+ Lithium Iron battery bank to increase storage that will eventually replace the lead batteries when they become worn out in 5 or 6 years.. My options I have been considering are separating the 2 Outback charge controllers so there is one for each bank with 2 Radian inverters that could sync their AC output however the way the panels are setup is one is for East South East facing panels and one is for South West facing panels but that seems doomed.. The other thought would be using the Mate3s logic and somehow switching back and forth between the 2 battery banks but the charge parameters are different so it is also doomed.. The last option I have thought about is either waiting till the lead batteries wear out then scrap them and change technology or change now and try to sell used batteries.. The L-iron cost per kilowatt storage has fallen below the lead acid and it seems a poor choice to add another 8x L16 batteries to meet my storage needs.. I have some 100a mercury relays but switching under more then a 400w load leaves the chance of a sustained arc and following explosion.. Manually doing the changeover would be a drag even if it was twice a day and that still would leave me with a charging dilemma.. If I went common buss and used the lowest common charge settings I guess I could squeak by without damaging the batteries but I would defiantly have to lock out equalization mode..