in case your site goes offline. What would the users do in case such an event happened?
In that case, all they can do is kick themselves for trusting an anonymous website with their money!
a custodial cryptocurrency wallet
By my definition, anything custodial shouldn't be called a wallet
(maybe with the exception of LN wallets in which some parts of the wallet are custodial). A wallet, by my definition, gives you and only you access to the private keys.
Anyone can of course choose to use an anonymous custodial service, but they should be very aware of the risks.
Depending on the user's needs, some people may like that an anonymous site owner can't be forced to follow KYC regulations. I don't like being forced to send a selfie to an unknown site to get my money back.
Nummix is a transit wallet with a dynamically adjusted service fee (the wallet is not intended for long-term storage)
There's always the risk of selective scamming (for some reason
some people send ridiculously large amounts to anonymous websites) or an exit scam when total deposits get high enough.
I do however like what you've built. I probably won't be using it myself though for reasons mentioned above.