Can I upgrade the elementary's ubuntu base to Ubuntu 16.10?? Will it be safe to do???
TL;DR: Yes you can. No you shouldn't.
Actually this is not exactly the same as "converting an Ubuntu installation to elementary OS" which results in a kind of Pantheon Desktop Environment-on-Ubuntu, the result of upgrading would be something like that as well.
So even if globally this kind of upgrade should be "safe", some bugs and glitches are likely to appear, so I would advise against it.