Mirror Column & Board Permissions

I work as a project manager for my company and as a PM is natural that I need to track and record items and deliveries across multiple internal and external teams and then produce a report back to the client on a weekly basis.
I have setup my PM board which will track quotes (dealt with by sales), in progress deliveries (tracked by my and other internal team) and an inventory section (Which is tracked by the in life team). Throughout the journey from quote to completed delivery I will have communications with internal teams that I do not want to share with the customer, this why I came up with a solution to mirror the cells and columns across to the customer board. However to enable the customer to see the specific information within the cells they require to be subscribed to my PM board which I do not want to happen as they will be able to view my internal communications.

Can a feature be added to the mirrored column, to enable the customer to view the shared cells and columns form my PM board rather than having to share everything with them?

A slight work around I have is to integrate the outlook app and use the “emails and activites” View to communicate internally as the customer cant see these unless I allow them too. Unfortunately I am currently selling this product to my company and we are nearly ready to sign off on an agreement(which means I cant integrate the outlook app yet) but this will be until at least April so my ask is if there is anything I can do in the meantime to put in place a work around or if you can enable the above feature request of allowing the information of a mirrored column without being subscribed to connect board.

Harry C