First off Thanks to everyone for their replies. I appreciate it. I have since purchased a 300 amp hr lithium battery from Canbat and a 3,000watt pure sine wave inverter from Renogy and also Renogy battery monitor. After researching much more than I expected I have come up with either replacing the existing automatic transfer switch with a 3 way unit or adding another 2 way ats at the front compartment for the generator and the inverter. Since a 3 source switch is rare and expensive I think that a second 2 way ats for the gen and inverter is the way to go. Any flaws that you can see in my plan?
https://www.amazon.ca/gp/product/B07RP5B5P7/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1https://www.amazon.ca/Renogy-1000W-Solar-Inverter-Cabin/dp/B07MKN7MM3/ref=cm_cr_arp_d_product_top?ie=UTF8&th=1https://www.canbat.com/product/12v-300ah-cold-weather-lithium-battery/I should add that this will be our full time home for the next 2 years as we build our house.