Inverter installation and automatic transfer switch

Ok, so found an AIMS 3000 watts PSW inverter w/ transfer $600.00 +/- not sure I want to spend that much.

In lieu of not installing an additional transfer switch and keeping it somewhat simple. What about connecting the inverter to the existing ATS shore power and installing a disconnect switch prior to ATS? So, if Im not using inverter its totally off from electrical system and avoid any damages in the event shore power or generator is energized.