Is there a way to load a sql script with a specified encoding into a running SQL Server Management Studio (SSMS)? Just as the question says. 
I have scripts with 3 different encodings and feel offended by having to manually select of about 200 possibles I was never interested in. ( I didn't count them ).
this might not be the answer you expected/hoped for but take a look at DbVisualizer. This is a nice tool that organizes sql scripts as bookmarks and we can choose in what encoding they are written to disk. The tool is multiplatform and multidatabase.
Using this I - as an oracle dba - can use a SQL server database without having any dedicated SQL server tool installed, from my macbook.
Choosing a smart encoding if you work multiplatform can help.

I hope this helps.