The technical problem is solvable, the deployment and technical support, and sales problem, and getting customers to upgrade, and the technical support, and did I mention the technical support problem would be a complete nightmare.
You can't actually leverage any of the economies of scale that you can get from building software, when you have to hold the hand of every single customer you deal with.
Someone like Oracle[1] can get away with this sort of thing (While charging an arm and a leg for it), but this is not the problem that your typical startup can solve.
[1] The other difference is that your Oracle database + solution is business critical, and businesses have no problem with paying $XY,000/year for business-critical solutions. Intranet search is a nice-to-have, and businesses balk at paying $5/user/month for that sort of stuff.
I have a strong feeling that Google Desktop Search had a lot of this sorted.
That was 10 years ago.
With all the advances that has been happening in the meantime and assuming businesses are interested enough to adjust a tiny bit to simplify crawling this doesn't seem impossible at all if a well-funded team started working on it.