gmaxwell - your holier than thou, coder superiority is not helpful, with you pull requests and shell histories.
It was not intended to be a holier than anything response. It was the frank, honest reason. Why isn't it done? because no one who wanted it done has done it, people doing things have considered other things more important. It isn't an idea whos usefulness had escaped attention, though that happens sometimes.
On the contrary, I could argue your tone here sounds rather holier-than, with your imperative "Please sort this out or show me a version of bitcoind that uses it already", and your essays on access, linked tables, and two line changes. .... but sometimes tone doesn't come across clearly online and I had no more intention of offending you than you did of offending me, I'm sure.
what difference does the BDB see if this file is outside the data folder?
You can only switch between the files when they've been cleanly closed. Desync of the wallet.dat and the other database coupled with an unclean shutdown results in database corruption which can not be automatically repaired.
most people don't have the time to understand the ins and out of BDBE, we just see features that we would like or things we'd like to change. Bitcoind is still a terrifying prospect to install and use for most mortals,
Not an argument against it, as I said I think it woudl be great (personally I'd use it to have wallet files on more reliable media than the block databases), but a walletdir is far outside of a "most mortals" feature in any case. As generally is plausible denyability. I'm always a little weary about brittle security: People are better off not having denyabilty and knowing they don't have it, then they are not having it and thinking they have it. Moving the wallet is a fine feature, but it does not achieve the goal of hiding bitcoin usage and shouldn't be advertised as such.