I doubt you are a fan of traditional centralized exchanges and KYC services but have you perhaps transferred the coins you got from Splash to such a platform to see what would happen or done any analysis with available AML bots to see how "clean" or "dirty" that BTC is and what its associated risk rating is?
I don't have the address with me right now, but as soon as I get hold of the wallet, I'll run an AML check out of curiosity.
To the OP, what about providing a Letter of Guarantee for orders?
i.e I create a order for BTC -> ETH, you'll provide a deposit address for my output address. Generate and sign a letter with the details so I can prove I should have received my coins if anything goes wrong.
Good suggestion on the Letter of Guarantee. We'll add that. Thank you.