Even more S-300PMU2 would be good for Iran, let alone S-400you see integrating Hawk into f-14 is old news from 80s iran abandoned that project and built fakour
by the way why you think Iran is interested in S-400
Shuffle the IADS with air defenses made from different countries like China does, they have their own but mix it with Russian systems
It is better to have systems from multiple sources mixed with homemade ones than only homemade, when its flaws will be shown to the enemy, you have nothing else to switch on