I don't think that exists currently. And even if it exists, I'm pretty sure that's a bad idea. While a lot of people here on Bitcointalk are bitcoin-only people, I'm pretty sure even the biggest altcoin investors would tell you that this is a really really bad idea. Just so much crap even in the top 20 alone.
Not yet, but I've seen a few DeFi early-stage projects that were building with this concept in mind.
Despite some people being against this, there are a few who can't or don't have the time to take the trading or HODL-ing in their own hands, and even the new crypto adopters will be eager on this option. The way I see it, before we know it we'll something like this become mainstream because it fills a market gap.