If you're going to have 500 (or whatever number) of runners per sex, just wipe out the time standards and use a descending order list that you have to run by (6-8 weeks before the Trials, or whatever the committee decides is the deadline), so they can sort out bogus times, potential lawsuits, times run wearing illegal shoes, etc.
That said, what city/running organization is willing to bid to host the Trials, knowing that it probably will be a money loser, despite whatever national publicity and money entrants and their friends/families will bring in the form of hotel night stays, rental car fees, local spending, etc., given that USATF/USOPC will tie the LOC's hands on what sponsorship they can pursue (i.e., Nike is a sponsor of both USATF & USOPC, so the local organizing committee can't pursue Brooks or ON, or any other competitor, etc).
Right now, the business model of hosting and staging an Olympic Trials marathon is broken. You want to lose $1 million or more? Ask the New York Marathon folks after they hosted the Olympic Trials in 2007. I don't even want to know how much the Atlanta TC lost on the Trials.
Personally, I'd rather go 100-150 based on descending order (no time standard), with anyone meeting the World Athletics Olympic Games standard getting an auto Q into the trials. If you want to have standards for athletes to try and qualify from either the 10k on the track or the 1/2 marathon, I'd base it on the top 25-30 times from 2022.
It's gotta be manageable for all parties involved.