[agarsev]

Sign language researcher here! I would recommend you look a bit at the scientific literature on the topic. I know it can be a bit overwhelming and hard to know to separate the actual info from the garbage, so I can try and select for you a few hand picked papers. IMO, trying to understand sign language oneself, or at least getting basic notions, is fundamental to understand where the real problems lie.

Unfortunately there's no getting away from that. While the scarcity of data indeed is an issue, and your idea is nice (congratulations!) the actual problem is the scarcity of useful data. Since sign language doesn't correspond to the oral language, there are many problems with alignment and just what to translate to. Glosses (oral language words used as representation for signs) are not enough at all, since they don't capture the morphology and grammar of the language, which among other things heavily relies on space and movement. Video + audio/audio captions is nearly useless.

Good luck with your efforts, this is a fascinating area where we get to combine the best of CS, AI, linguistics... but it's hard! As I said, let me know if you want some literature, by PM/email if you want, and I'll get back to you later.