Beast Machines was already underway (so had been at least 18 months in development before that) before Archer took on the lead role of Hasbro Transformers Design. And even still, that wouldn't high enough to make a management/corporate decision to move from one style/series (Beast Wars) to another (Beast Machines). He was obviously able to convince the higher ups to take on the Unicron trilogy idea of his, but only his more recent position would be able to dictate what series starts and ends... and even external forces (the creation of the HUB) forced an end to Animated so that the new channel had a new TF series.
According the the tfwiki article link, and from my own recollections of his Hasbro title at the last 6 or 7 BotCons, he's been promoted through several management levels just about every second year... and I think it was the tail end of the Unicron Trilogy that he was high enough to have some say or power in the direction of future TFs series/toylines (outside of the Movie & the HUB decision).
The creation of Beast Machines as a series would not have been one of them, as he was just one of the team of regular toy designers at that stage.