[NWChen]

Modern batteries
Sealed lead-acid batteries are heavy, have poor energy density, and have a shorter lifespan than lithium batteries. For the high-amperage, high discharge rate application that FRC usually presents, I hope the standard SLAs can be phased out in favor of newer battery technologies.

pilleya has a good point about fire safety though - FRC's success is heavily reliant on its ability to keep participants safe, and until lithium batteries can become less dangerous their arrival is understandably far in the future.

Usable simulation tools
Gazebo/FRCSim's low-profile debut in 2015 was disappointing - I saw more threads on CD about installation issues than usage questions. Catalyst/similar games are useful for understanding the field, but don't effectively allow teams to consider the potential designs and strategies of different robots during alliance play. A low barrier-to-entry simulator which combines accessible 3D modeling and good interface design could increase the level of play for many (especially low-resource) teams.