That is related to one of mine: an email/messaging client that doesn't suck. Or rather, multiple clients based on libraries for ‘mailboxes’ of various kinds (including those in which messages appear asynchronously, like mail and messaging servers, RSS, usenet, scrapable web forums, and so on). I don't know how continuous AV links would fit in this framework, though.
Another five-year software project I'd have fun with would be LLVM front ends for various historically interesting programming languages, and likewise code generators for dead or niche processors.
If I also had money for expertise and prototyping, I'd like to make a keyswitch that feels like an IBM Selectric (or at very least an IBM beam spring switch) but fits ISO's thickness requirement so that it's salable.
Another five-year software project I'd have fun with would be LLVM front ends for various historically interesting programming languages, and likewise code generators for dead or niche processors.
If I also had money for expertise and prototyping, I'd like to make a keyswitch that feels like an IBM Selectric (or at very least an IBM beam spring switch) but fits ISO's thickness requirement so that it's salable.