As per the Process for reviewing classic confinement snaps you need to describe not only why you believe classic confinement is required but also then detail which of the criteria for classic confinement your snap fits within. Then we need to determine if the snap fits within one of the supported categories for classic confinement.
However, I am a bit confused here about the errors you mention with strict confinement for your snap - can you provide details for how this can be reproduced and I can try and look into it - since the error mentions the process is unconfined which seems odd - is mmcli part of the lenovo-wwan-dpr snap? Can you please try and explain more what the setup of your snap is and what it is doing and I think we should be able to get it working under strict confinement.