If your battery inverter supports AC coupling, should be easy to add a GT PV inverter that works with it. GT means it synchronizes to AC line (your inverter) and adds current while following voltage.
That should mix-n-match with your existing DC coupled equipment, can be economical, and adds AC output power.
e.g. you might find a Sunny Boy 5000US for $500, $0.10/watt. It would probably get two strings of PV panels (small gauge wire, no fuses needed), and add up to 5000W to available AC during the day.
Even new model GT inverters may cost only a bit more than another Conext XW MPPT 100-600, and deliver additional AC at higher efficiency (compared to PV --> 48VDC --> AC)
Your XW Pro is an inverter/charger, it already will draw AC from grid or generator input as needed to charge batteries. With GT inverter on its output, it will draw from there.
The additional feature to support AC coupling is that it will raise frequency above 60 Hz to say when it wants less. Mine settles somewhere between 61 Hz and 62 Hz, to get something between 100% and 0% of available PV converted to AC.
If your inverter + SCC already commands SCC to reduce output as needed to regulate charge current, you would also be fine with just DC. If your inverter does this without a battery shunt, it may be the inverter measures its own battery current and communicates with SCC for its battery current, and adds them together. So if for instance you programmed 40A max charge current, if inverter was consuming 10A it would have SCC deliver 50A, leaving 40A for the battery. This would only work without unmonitored currents like additional loads. (My SMA system can work without a shunt if only DC coupled SCC like Midnight Classic that it talks to, or with shunt for arbitrary sources and loads.)
With a lead-acid battery, there is a preferred charge rate. My AGM do want at least 0.2C, otherwise need longer absorption time. FLA may want 0.12C.
When you put in LiFePO4, it will probably accept 0.5C maximum, but only around 25 degrees C. BMS should implement low-temperature charge cutout, perhaps at zero degrees C. However, 0.5C charge rate is too high when cold, needs to be something like 0.1C or 0.15C down around 10 degrees C.
I haven't heard of BMS or SCC that adjust charge current according to temperature. What I would do is program SCC/inverter for a maximum charge current of perhaps 0.15C or 0.25C, and set a higher temperature charge cutout compatible with that current.
You want all available PV harvested by SCC (or GT PV inverter) and delivered to AC loads, while regulating battery current to what is desired. Most systems with separate DC coupled SCC can't do that, but apparently Conext can. Victron can do it with a battery shunt and controller (should work with any inverter.) Hybrids should do it because they contain both SCC an inverter, can measure battery current. AC coupling can do it because inverter/charger knows battery current.