I don't have to provide a "proposed solution" to MITM; the proposed solution is "stop that". To the extent MITM is getting harder, that means network protocols and software is getting better.
This is like asking the makers of adblockers what their "proposed solution" is for ads, or asking the makers of spam filters what their "proposed solution" is for sending spam.
Most critically, in a standards body, the right answer to people trying to MITM is a polite and diplomatic version of "go away, your use case is invalid".
> If you do not think private companies and businesses have a right, and sometimes an obligation, to secure and monitor the traffic on their networks
They can certainly try (currently), and one of the jobs of security researchers is to ensure they fail enough that they stop trying. I also hope one day that there's enough collective bargaining power among engineers that such companies cannot successfully hire people, and that nobody ever has to be desperate enough to accept such a draconian network. I'm glad I'm in a position to be able to say I'll never work for a company that requires MITM; everyone should be able to avoid that. And the only time I'm aware of a company having an obligation is due to misguided regulations on certain narrow classes of businesses.
> MITM technologies are a societal risk more than a benefit
The company is the only one who could possibly benefit, and that's leaving aside the likely possibility of doing more harm than good; security measures work better when your users want to help you rather than thwart you. Meanwhile, the societal harm of ever allowing MITM is massive.
Right now, the biggest step I'd love to see happen is browsers (in concert) having a persistent banner for "your traffic is being MITMed" any time they're getting the wrong certificate for sites, and browsers making that impossible to remove without rebuilding the browser from source (which is a substantial barrier). Next, we can make it easy for sites to detect access from MITMed networks, and make policy decisions on that basis. Then, coalitions of sites can collectively make it expensive to MITM.
Put that together with new protocols that are increasingly desirable, and increasingly unavoidable, and which users will want, and you have a recipe for substantially reducing the number of companies willing to even try to MITM.
> then say "You can block spam and outbound attacks without MITMing traffic."
"We block outbound email ports" is not an unreasonable policy, as an example. And if someone tunnels around that, now they're spamming from their network, not yours, so it's not your fault.
> How do you propose DLP gets accomplished with zero access to the network?
"DLP" has become equated with "MITM". But you could, instead, focus on access to the data rather than interception of exfiltration. If people are trying to exfiltrate your data, they will find a way, very very easily. And there are much better ways to catch accidents. Also, most companies are still at the level of avoiding headlines like "laptop stolen with our whole database on it", which has nothing to do with MITM.