Amazing! I've independently done nearly the same thing. My setup uses full size Pi models 3, 4 and 5. They're networked on a 5 port switch. For the record, the PIs use about 3 watts each. The power all comes from LiFePo4 batteries via a 6KW inverter. I also have a dynamic DNS updater that runs on cron every 10 minutes. I've had this running production websites over a year, nearly 2 years. I get a 99.9% up time. I do have an external monitor that runs on a different computer that tests the sites to ensure everything is working. I get a text message if any of my sites go offline. So yea, it's definitely workable.