Is it possible to build a "no dependency" client? Just integrate all (and only) necessary external codes, e.g. SSL, so people can build it without depending on any package.
With this code, just getting rid of boost seems quite impossible.
LevelDB - one would need to create a new db engine, from scratch, wanting to get rid of this one.
But LevelDB is an internal code already, so I guess it could stay. It's a fairly simple one and easy to audit.
As for OpenSSL - I guess you could embed the hashing functions into the code and use the ecdsa functions made by sipa.
The rest (berkeley, upnp, zlip, png & qr) should be much easier to remove.
EDIT:
Oh, wait... WTF is protobuf?
You guys are not giving up adding more crap in, are you?