Sounds confusing. If you keep your wallet offline and you use it to create transactions what is the purpose of another device? All you need is the mk4, a micro sd card & a laptop. I have no idea what you would need a Raspberry Pi for.
Discussion
Being extra paranoid about creating psbts and broadcasting it with a single portable device smaller than a laptop. Its just to use the device for that one single purpose. But yea you're right its a bit redundant.