4. Stick with a series, not a movie
When Variety reported on a potential Aegon the Conqueror spinoff last April, they shared that HBO was considering making a movie that would lead into a series about the conquest. Not many details on that idea were ever revealed, but my first reaction was just... why? Making a theatrical release Game of Thrones movie would no doubt be epic, but a movie and a series would be a little self-indulgent, don't you think?
Unless Warner Bros. did a two-part (or even three-part) movie as they've done with Dune, I don't think this story could work on the big screen. To me, adapting Aegon's Conquest in live-action as a show is the perfect way to do it. Let's not get too ambitious with a multi-medium release here. Game of Thrones is one of the greatest series of all time, and House of the Dragon is off to a promising start on TV. If it ain't broke, don't fix it!
3. Don't make us hate Aegon
There are some hateable Aegons in Westeros history (ahem, Aegon II Targaryen above), but that list doesn't have to include the very first! Because George R.R. Martin's book Fire & Blood is told as an unconfirmed, second-hand telling of history written by an archmaester, HBO has a lot of freedom to take creative liberties when adapting the text to screen. This has happened with House of the Dragon, and we'd imagine it would happen with an Aegon's Conquest show as well. And while no characters in the Game of Thrones universe are black and white, it'd be nice to actually like and want to root for Aegon I Targaryen, who would presumably be the protagonist of the series.
The reason for my concern here is a tidbit of information we got from The Hollywood Reporter in 2022, as part of a feature they did on scrapped and planned Game of Thrones spinoffs. According to this report, there was a plan for an Aegon the Conqueror spinoff before, written by Rand Ravich and Far Shariat, which would depict the character as "a drunken lout." Yikes.
Now, I've never thought of Aegon I Targaryen as a perfect ruler, but we've heard a lot of good things about him and this is such an important part of the story. I'd hope a spinoff would at least treat him with respect, even if he's got his flaws.