heres my list of things for halo 5
firstly if it has anything to do with the flood please include the infector from that was going to be in halo 3 (http://halo.wikia.com/wiki/Flood_Infector_Form)
as well as the G4H-DuSH (gah-dush) wich again you removed from halo 3 (http://halo.wikia.com/wiki/G4H-DuSH)
as well as the falcon fighter not the falcon from halo reach which im pretty sure everyone has heard about heres a link just in case you dont know what im talking about (http://halo.wikia.com/wiki/Falcon_%28Fighter%29)
and heres a few more things
many of the halo wars veichles but driveable (excluding the vampire)
as well as the hunter`s assult cannon can be removed and carried around like a support weapon but requires a few seconds to fire as it does on hunters
also maybe a promethian support weapon
and a human aircraft for multiplayer
as well as a few new veichles (both unsc and covenant)