The other answers make several excellent points about the super brain's failure to reduce absolute R&D time on all the component parts of an Iron Man suit.
However, if a non-imprisoned Tony Stark wanted to make such a suit from his office under no physical duress, the tactics involved would likely be primarily the purview of his super-brain:
- Quickly generating a list of required components for the suit
- Identifying any components for which the technology did not exist
- Locating all of the patents, companies and people worldwide needed to create these "sci fi" components in the fastest manner possible
- Recruiting, purchasing, or licensing said personnel, materials, and organizations in a friendly manner
- Tricking/coercing any unwilling partners as needed by quickly determining their vulnerabilities and exploiting them
- And of course, all the while, sectioning off a small portion of brain activity to make the required financial investments and other business/social moves to generate the necessary funding and connections to pull everything off without significant competitor/government intervention.
Ultimately, whether you are a "regular" super-brain, or a comic hero like Tony Stark, you cannot actually invent/create everything on your own. Rather, you must use your "brain powers" to:
- manage a huge number of simultaneous initiatives at the highest possible levels,
- possess (and continually develop) a huge store of functional knowledge across almost every imaginable field,
- and quickly identify, vet, and persuade a great number of the world's best and brightest people to work on a challenge that in most likelihood cannot be fully or openly revealed to any of them.
Given this answer, it should be far less odd that Tony Stark is portrayed not only as brilliant, but also a party-loving playboy: super-brains make super-schmoozing that much more important and valuable. A lot of the most brilliant SV Tech CEOs could probably take a lesson from that.