On few occasions when I get to this step on most fiat online casinos around my country, what I often used as source of funds could range from statement of account from banks.
My question is can we use crypto wallet with long history of transactions and possibly a sign message be used as source of funds requirements for online crypto casinos?
But unfortunately, at the moment, I do not think any casino is currently accepting a wallet as a prove of fund, and this is possibly because any body can use another person's wallet transaction history as their own and the casino won't have any means of telling if the wallet used actually belongs to that user or not.
You might want to say that this is where the signed message comes in, which I personally agree with you on, but then and unfortunately again, no casino I know of, is or will accept a wallet's transaction history as a prove of fund, maybe this can be possible in the future as the industry becomes more mature.
We may have many factors that could limits that possibility, and for sure crypto address also have it own limitations in terms of transaction tracing and verifications since most cryptocurrency transactions are without lebeling.
Unless if the company you work for are paying and making right payment reference to indicates that this is a salary payment so that the verification team can take a look at it before validating and approving it.