Can I get batteries installed on a later date by a different installer or will it void warranty with current installer?

I am about to sign a contract for 12KW grid tie system. We didn’t have pge power outage in the past 7 yrs so we decide to go with grid tie system and add batteries later when there is a decline in battery prices. In this process I learned that grid tie system will not produce electricity during power outage and require either batteries or Enphase sunlight backup. Since Enphase is advertising that IQ8Ms are compatible with Sunlight backup, I inquired the installer and seems like it requires 6-8k retrofit equipments. That’s a lot of money for a non battery system intended to keep solar production ON during an outage. I looked into cheaper LiFePo4 alternatives as they should be enough to keep my system producing during an outage but the installer wouldn’t install those batteries. On a later date can I work with an installer who can install LiFePo4 batteries or will it void warranty with current installer?