I've been looking into those Avago/Broadcom dot matrix displays recently. I don't think it'd be too hard to recreate something similar with tiny SMD LEDs on a PCB and a slightly intelligent driver board, for much cheaper. Would there be a market for something like that?
Only if you can get them listed at Digi-Key/Mouser/etc. Even if it's under a "maker" brand like Adafruit, Sparkfun, etc. Anyone who can replacement TIL311 and friends displays in there, and advertise them, will sell quite a few.
They're not hard to make, but they're the sort of thing that no one really wants to make in-house, since they're a means to an end rather than an end in themselves. Great thing to sell, though!
In grad school I taught a electronics lab class where the students would burn through a bunch of HDSP-0772 every semester. I thought about coming up with a replacement, but at the time you could still get them for a somewhat reasonable price (like $10 or $20?).
At today's price of $50 it might be cost effective to do as you say, but I imagine there's not a huge market.
