Here's what happens, in a best case scenario where this is actually a legit offer (it isn't). They log in, the flag is raised immediately. Different location. Even with VPN, it's a different type of IP. That's the first flag. Then they place a bet, different markets to what you normally do. Second flag. The amount even, of the deposit and the bet. Third flag. If you have high limits, you either have a personal connection or are fully KYC'd. These flags will lead to an investigation. There are other flags down this road. You will lose access and/or get limited.
There are worse case scenarios. Most importantly what Eternad's pointed out (why are they using you and not themselves?).
Still sound good?
If we're speculating, I'll try it too.. Of course, I'm almost certain it's money laundering, but we can not be 100% sure.
I once met someone who, even though they were aware of the risks (that it is money laundering), wanted to do it anyway because they were in financial trouble.
I think those who posted this offer are mainly hoping for a response from such people. Perhaps they're addicted to gambling and are having problems because of it. Just like a person I once met.
Referring to what you wrote, I think they can work around it. That's why they write about renting – when the casino notices anomalies and launches an investigation, the owner confirms all their details, and the account continues to operate.