"Sick" as in "slick?" "Good?" (Going to add "clueless oldster" to the description on my BH profile page).
Along the lines of a "Fediverse Amazon", @petrescatraian@libranet.de told me about flohmarkt, which does look interesting. One of its instances can be viewed here.
One note on "sick" being slang for "good": that particular slang started in the 80s, and some of the younger generation consider it to be old person slang.
IMO we need to break it in a few independent but cooperating decentralized systems;
A transportation service where consumers will request the transportation of goods or people from point A to point B, and providers will make bids for those requests.
A storage service where providers will offer storage of goods at specific locations, and consumers that make requests for the storage.
A LC service, where two parties can enter an letter-of-credit (LC) contract, and providers can guarantee the contract.
If these systems are available, it would be possible to implement additional decentralized services like;
Why? Is it bad providing alternatives? Especially as it is Fediverse based, which is federated and not controlled by a single company. And being compatible to Fediverse protocol means you can use any application.
Imagine something like Amazon, a central place you go and everyone who federates with it can sell products. I'm not against it.