Several years ago I had this experience.

At the end of the second interview I was asked the question how did I feel about having a younger person as my boss, the idea that I might have any issue with that had never even occurred to me and I said there was no issue.

I didn't get the job, the boss who was an Asian female in her (I'd guess) early thirties was the only one with an issue, my guess is its a cultural thing.

Now days I run a team of folks of various ages, my boss is younger than me though, not by that much mind you.

As usual YMMV

I tend to agree, the arbitrage scenario would require you to be able to have a private network to detect the price variation between the markets and do the trading, while you are doing that you'd have to change everyone else's feeds latency.
I'd suggest that existing market surveillance would almost certainly catch this, whether it was classified as market manipulation would depend on the regulator but if they could show you'd tried to manipulate the latency of other peoples feeds I wouldn't want to be in your shoes.