Merging BS4 Theme with Sage 8.5.0

So I grabbed one of the BS4 themes and was wondering what would be the best way to merge this with Sage. I ended up doing the following…

As it stands I’ve dropped the theme files into assets/styles/bs4 and then included the main theme sass file into assets/styles/main.scss.

I then deleted assets/styles/bs4/bootstrap and pointed the theme variable.scss to include bootstrap variables from…
@import "…/…/…/bower_components/bootstrap/scss/_variables.scss”;

The Sage variables.scss overwrites the BS4 theme variables so you can still edit and build out your sage theme as you normally would.

I’m pretty sure this isn’t the most efficient way of doing this, so I’m posting as a guide but also for feedback on a better approach. Would that lay with the merging of the gulpfiles I guess?? Any input much appreciated.