Is there any mod that let you build a Base around Vault 111 or inside of it ?

Not yet, there likely will be once the GECK comes out and people have had time with it.

At the minute, it's a little limited what can be done with the tools available.

My understanding is that you can turn any place into a base simply by summoning a workshop to that location.

https://www.reddit.com/r/fo4/comments/3tap39/psa_console_command_of_playerplaceatme_c1aeb_will/