I'm not a huge fan of this line. The vendor-bundle is really a big hack that should be changed. It was necessary to get Key working in the browser, and exposing some extra pieces of it was necessary for BIP32. However both of those features were very important that we needed urgently (Key was so bitcore would work in the browser, and BIP32 was for the multisig wallet). I don't see as much urgency for Armory style key derivation. Maybe it would be better to take this opportunity to improve the crypto interface of bitcore rather than introduce further technical debt. (See https://github.com/bitpay/bitcore/issues/186 )