Is there a way to use a Thunderbolt monitor with Bootcamp (WIndows 7) and not need to restart each time it's connected?
Yes.


  Thunderbolt hot plug is supported under Windows 8 or 8.1 on all 2014 and later Mac computers.


No - if you run older OS or hardware. In that case, this appears to be something you have to live with. The options are running Windows in a virtual machine so that Apple’s OS X drivers handle the hot plug for you or interrupt your workflow to accommodate the Windows drivers. Sorry, but I've not seen any other options so far to address this.  

Reference: https://support.apple.com/en-us/HT204154