Depends how the solis module handles the additional data.
RS485 is a multi drop system, so it should work electrically.
Worth a try.
Otherwise you could use some of the pi pins to switch a relay to disconnect the solis when logging
Or just sniff the solis data!
Yes that is what I will try, first need to order the cable, but I did just come across this pi RS485 HAT which looks a bit neater and I assume it should work except the /dev/ttyUSB0 will probably need to be changed to the serial port equivalent.
/dev/ttyUSB0