it can import a private key.
I'm looking at it now (I've never chosen the 'use imported addresses' feature in the beginning, the other modes don't have importing menus).
I'll see if Electrum can work with a few hacks. If it does, I'll test it with a couple of thousand watch addresses / privkeys.
You can use the importprivkey command line function to import private keys into the wallet.
Also, for notifying from electrum, I think it is possible with the addition of another software. See:
http://docs.electrum.org/en/latest/merchant.html#add-web-sockets-support