Iran can't fly most of their F-14s. They don't have the spare parts to keep them operational. They have at most, a single squadron active, but they would be no match for a fifth generation fighter, let alone the vast armada of fourth generation fighters still out there. They would be more likely to resist NATO with a Soviet or Chinese design.
Sure, but the plot doesn't have to acknowledge reality too closely. The original didn't care too much about it and worked just fine. A quick off-the-top-of-my-head outline for a possible Top Gun 2:
- Maverick & Charlie married, lived happily, and Charlie ended up working in the UN in some moderately high-level capacity. Their son ended up a USAF pilot, like his grandfather.
- After Gulf War II, Charlie ends up liaising with the US military in Iraq during the insurgency. She gets killed in a kidnapping; make it a failed Special Forces rescue operation or something like that to keep it topical.
- Mav loses the plot after the funeral, like he did after Goose died, and ends up going to the Middle East to see where she died. He ends up working for some mercs out there to keep busy and try to forget her (think of Cruise's character at the start of Lost Samurai)
- Do all the above pre-credits and then bring things to the present day.
- At the start of the movie proper, have the Iranian F-14 squadron taken over by a rogue element in the Iranian military as part of wider coup attempt. Mav's merc operatives get hired by the rogue element, partly to help the coup but also because they know Mav has F14 expertise and want him to train their pilots.
- Meanwhile, his son is part of the US forces in the area. Iran suspects Israeli and US support of the coup. The US doesn't want WWIII to break out just yet and offers military support to Iran, figuring there's a diplomatic opportunity here as well as a crisis.
- Mav and his team ends up having to fly F14s against his son's squadron, without realising who he's up against. As soon as Maverick realises he's up against US forces, he attempts to call his guys back, but they get shot down, fast. Mav attempts some extreme maneouvres to avoid the superior US forces, and almost manages the impossible, just like he did in the old days. Until a mechanical failure forces an eject... and gets killed, like Goose did. All this can be done within the first 20 minutes of the movie.
- Now focus the movie on the son. You could start it off with a series of relatively easy missions quelling the coup, setting up a competitive relationship between him and the new Iceman.
- Then have him discovering (from a captured merc?) that his dad died in the conflict at the USAF's hands
- he struggles to cope, rebels against the USAF for a while... and then the official investigation proves that his main rival and Iceman-analogue in his squadron colleague was the one who shot down and killed his father. Have that guy defect to Iran for a bribe with a few other guys, and MavJr having to shoot him down in the big final showdown to prevent the defection to the Iran
- End with the attempted defection being hushed up to prevent a diplomatic incident, but MavJr being offered the posting of his choice by way of compensation...

Easy box office gold, right there.
