I don't know that this would prove anything. Regardless of the encryption method you suggest, we must still trust that ChipMixer's code running on their server is the same code made available for public audit. Without being granted access rights to their server (which I can't imagine happening) we're left taking their word for it. Like we're taking them at their word that they are not logging.
Yeah as I interpret it, this would be more of a release of the frontend (mostly) and might not go very far towards proving openness as you'd still have to trust ChipMixer's daemon thats running on the same and the different server.
A mixer shouldn't be the only place you go to mix your coins in order to make it more private, sending funds to certain exchanges, mining rentals and gambling sites are often good additions after and between mixing. There are probanly better ideas others have come up with that I've missed, large companies holding bitcoin on a large scale aren't going to care too much if a few bitcoin go in and out every so often - some exchanges are better than others will be so remember to research if you want a good strategy.
On the Ddos issue if ChipMixer were to put into development a system where you download something and get a public private key pair you can then use to connect to the site over cloudflaee so it's still encrypted however there are a few main issues with this: most people mixing don't want people to know who they're connected to and that they're using a mixer, why should you download something from an anonymous source (even if you trust them it's still a bit risky) most devs in bitcoin for example have compromised their identity this can't be done here... If a decentralised anti ddos system gets put into place then these problems can be vastly mitigated but even bitcointalk goes down when it's heavily ddosed and behind a cloudflare package so it might not actually do much...