At the moment, the filmmakers working on Thor are trying to create Asgard with miniatures and matte paintings, so I'm not sure which other Marvel IP's could've still been made in the days before CGI.
If Columbia pictures can convincingly make Superman fly in 1978 then Disney could probably make Iron Man fly around convincingly in 1984.Now that you mention it, I'm not so sure either.
Since it's the 80s you could make a cold war plot with Crimson Dynamo and Black Widow.
The plot could be similar to the OTL movie of Tony Stark getting captured and building the Mark I to escape. (Except this time he's captured by the Soviets and taken to North Korea.) Tony Stark makes improvements to the suit and making banter with JARVIS, Pepper Potts, and a blonde woman named Natalie Rushman (Who's actually Soviet spy Black Widow, who's been giving the Soviets Starks tech and aided in Stark's capture). Nick Fury and S.H.I.E.L.D. tells stark there's a Soviet spy in his close circle making Stark think twice about his trust of Pepper Potts and Natalie Rushman. It ends with a climatic fight with Tony Stark fighting the Crimson Dynamo and Nick Fury fighting Black Widow. Tony Stark defeats Crimson Dynamo and destroys the Soviet base recreating Stark's tech, but Black Widow escapes capture.