This will completely isolate the current regime. Cut the safety net of the IRGC, and close the tap of money, effectively this will reduce close zero the money flows tha sustain all this and make the system very likely collapse.
Why we don’t do it? I guess oil sales to India and China are a good starting point. Then there’s the support to Russia with weapons and tech for Ukraine ‘special campaign’, and let’s not add the fact that a destabilised Middle East is so convenient to so many.