Need to modify my main panel

Hello all. Thank you in advance for any guidance. I am in south Florida and I am a DIY person. About a year ago, I hired an electrician to install a new exterior main breaker panel and also a new sub panel in the garage. The house was built in 1975 and had aluminum service wires. The electrician did a clean job. Yesterday, I purchased a 15kw generator and I want to wire it into the exterior box. Unfortunately, my electrician wired the panel with the FPL feed going to the bottom of the panel. The top of the panel has the 200 amp breaker, and from there, the wires do a home run to the sub panel in the garage. If I install a 60 amp 2 pole breaker (for the generator to feed the panel) into the exterior panel, it will be positioned between FPL and the main breaker. In the event of a power outage, I cannot protect FPL linemen from a backfeed. I will not wire it this way. From my perspective, I have two options. 1. I can buy and install new service wire from the FPL meter, into my exterior panel and connect the two 110 wires to the 'top' of the panel directly into the 200 amp breaker. Then, I could connect two 'extension' wires from the bottom lugs, up to, and connected to the (already cut to length) service wires for the home run to the sub panel in the garage. A guy at Home Depot said that splicing these wires is a bad idea, as they need to be a continuous run. Idea #2. I could remove the two screws holding the plastic plate to the exterior box and flip the whole plate upside down. Then reattach the wires where they land. That would put the FPL service into the 200 amp breaker and the feed to the sub panel connected to the two lugs. I prefer this idea, but the Home Depot guy said that altering a panel is illegal or dangerous, etc. Thanks for indulging me. Standing by for comments. Thank you all.