Manny Coto and others involved in the production of Enterprise have mentioned that they planned to make Shran a member of the bridge crew in season five. Their motives are pretty obvious: Make a popular guest star (and the excellent actor who played him) as involved as possible. In Coto’s own words, “get Jeffrey [Combs] Somehow.”
The question for me is, why would Shran have been willing to take up a (presumably subservient) position aboard Archer’s ship? Shran is frequently shown in command of Andorian Imperial Guard starships, which gives him significant practical and political power. He is clearly a man of action, and strongly dislikes feeling indebted to anyone. He certainly does not strike me as someone inclined to surrender a command position.
So, how could Shran’s intended presence on the bridge of the NX-01 be explained?
Maybe they could have worked Shran in as some sort of observing diplomat. Only taking orders and doing work if it’s an emergency situation, but otherwise just there to take notes on the pink skins and learn about their culture. And we would of course also learn about them. Idk, just off the top of my head.