The problem for me is that the one level upgrade is the same from Gold (a very easy level to attain) to Diamond. So there isn't much of an incentive to spend more money in Accor hotels if you're going to be treated the same whether being Gold or Diamond. On top of that when using SNUs, you're essentially paying (in the form of vouchers) for an upgrade you should be receiving for free anyway. Personally I've rarely noticed a difference in upgrades between Diamond and Platinum, even Gold. And even as a Diamond I've had hotels be more interested to upsell me an upgrade to make more money instead of showing an appreciation for my loyalty, which feels cheap.

I think a two level upgrade for their highest tier members would be a reasonable expectation and make Diamond more meaningful to strive for.