Herein I argue that the game would be better off without them.
Drifters die easily, and seem to only serve to delay the construction of buildings for the alien team.
Allow the Alien Commander to place structures wherever there is active, connected infestation. Structures would grow slowly over time, but could be sped up by Gorges. This allows the build mechanics for each side to be more similar, while still distinct, and encourages Gorges to coordinate more with the alien commander.
Hives, I imagine, would require infestation nearby to be placed, and would be built in the same way. To compensate for the amount of cyst-chaining that would be required, Hives could be altered to cost less (50~). As with other structures, Gorges could speed up the construction, and I imagine increasing the unattended build time would be a reasonable tweak to compensate for the lack of drifters.
It has always struck me as odd in NS that marine structures appear out of thin air, whereas alien structures (in NS2), despite spreading infestation, have to be sent and deployed from a hive. It seems backwards.
Secondly, since Drifters serve no other purpose (unlike MACs, which can weld and group-build structures), there won't be any great loss of functionality for the Alien Commander.