If you give a human a "compliment sandwich" they are likely to take the compliments and throw away what they don't like. It will weaken your intent behind initiating the dialog.

A commitment to positive regard and support from your side is fine, but the way you expressed it in your examples feels manipulative and will lead to future compliments and interactions feeling inauthentic.

I've preferred to call it a "feedback sandwich" in the past but that feels like cop out management from Office Space, like firing someone on a Friday to minimize backlash.

If we're talking about a place of work then I might sandwich it by implying their skill is needed and, hopefully in a skillful way, that I like having them around. If these are the issues needing to be addressed then that's what makes it a "shit sandwich".

At the end of the day, I am responsible for only my own emotions. I can truthfully express what our relationship means to me and thereby provide some contextual buffering that they can rely on, if they want, but I don't want to push a desired reaction down their throat. That's a problem with an appeal to their kindness.