[dredmorbius]

Few of Iran's neighbours are in a position to do this.

Afghanistan? No. Lacks means, motive, or organisation.

Iraq? Probably not, despite past history of conflict, too much internal strife.

Turkmenistan? Very unlikely.

Pakistan? Has the capability perhaps, but little motive AFAIU.

Azerbaijan, Aremenia, Turkey? Again, unlikely.

The most likely beligerents would be Israel (already involved, but not seeking occupation in all likelihood), and Saudi Arabia. But both those also seem unlikely. Both benefit by a weakened and submissive Iran, but occupation would be an extraordinary undertaking and highly problematic.

Non-bordering countries might be considerations (India likely tops that list) but again the upsides seem slight given costs.