Concept: a sorta darker more fucked up paranoid Ford experience where Bill takes full advantage of the brain rewiring thing. Ever determined to make sure Ford stays isolated entirely, he makes sure he can never properly reach out to anyone.
Because he can’t speak any human languages. Instead, Bill swaps around his language centres so that he can only speak, write and understand Euclydian. Just making it so the brain swaps anything it comprehends in for his own language before it processes.
Now of course, Euclydian is a dead language - and Ford is now the proud only other speaker aside from Bill - making Bill consequently the only being in the multiverse he can talk to. At least unless he manages to re-code a universal translator to work with Euclydian god knows how far into his portal years - assuming he enters the portal at all.
Ford, ever the clever bastard, manages to get his postcard to Stanley regardless. He can’t write the address obviously, but what he can do is go to the postbox in the woods and ask it to ‘write the following message in English’, then tape whatever it outputs to the back of the postcard and just hope it did it correctly.
Naturally, it did. And Stan arrives to a Ford who cannot understand him and is speaking in literal colours, somehow. He’s also very insistently shoving a book at him with a desperate expression.
Not sure entirely how that situation would go down per se.