A player isn't required to look at his hand, he's only required to act in turn. If he's under the gun, then he's in turn. I can't think of any reason there should be a problem with him setting his chips out prior to the deal as he's only putting himself at a big disadvantage.
I have seen this played out in what is intended to be an entertaining manner: Before the cards are dealt, the UTG says he going all-in blind. Someone asks is that binding? Others laugh or make other jokes. If the dealer simply ignores the jocularity and proceeds with the deal then UTG might shove or fold in turn, once he sees his hand, and nobody usually complains.
The problem, as the OP points out, is finding a TDA rule that answers the unanswered question: Is this binding? The OP talked about betting with chips that looked like a straddle. Above, is what seems to be a verbal declaration. When is it binding?
22: New Hand & New LimitsA new level will not be announced until the clock reaches zero. The new level applies to the next hand. A hand begins on the first riffle, push of the shuffler button, or on the dealer push.Can the last sentence in Rule #22 be taken out of context and used to establish when a hand begins as far as verbal declarations or other forms of betting? If yes, then what about Action Out of Turn?