alt Hacker NewsOne interesting approach to this is the gas auction system in DeFi where (on Ethereum) traders bid to have their trades included first in a block, and that additional payment is burned / accretive to ETH holders. Though that turns "fastest connection" into "highest bidder" advantage.
Another approach that Aztec and some others are taking is to shield all transactions with zkSNARKs such that the intent of a transaction isn't known until it's completed. Combined with deterministic block times you could force random ordering of transactions in batches, effectively mitigating the fastest connection OR highest bidder advantage.
The real question is whether we even need stock exchange organizations if we can do it all on chain without them. I think the only thing you really need is someone to handle the stock ownership credentials in the event that legal action require involuntary transfers, that sort of thing. That could be a much smaller footprint organization, I think.