Add an additional "Compare all" button to compare all projects in the actual "Look in" folder. Show a simple is equal/different indicator on each project for the results.

Consider using VS-style solution files or kind of meta-scp.

This is somewhat similar to https://redgate.uservoice.com/forums/141379-sql-compare/suggestions/13517250-auto-compare-after-oping-a-project-mass-compare