Ingenuity was designed to fit under the rover, and occupied the available volume pretty completely. Check out the video of how it was deployed. Even if a multip

Ingenuity was designed to fit under the rover, and occupied the available volume pretty completely. Check out the video of how it was deployed. Even if a multiple deployment system could be designed and the budget was available, there would probably need to be changes to the rover (which is based on Curiosity's design), and these things tend to make cost and complexity balloon. But, redundancy would be nice -- Mars Sample Return helicopter proposes a pair of helicopters.