I'm not saying Summoner's should have Primals as a permanent pet that would a disaster but they should get an ultimate summon which temporarily evolves the Egi into its parent Primal. Also the Summoner should be able to command the Egi to cast a elemental aoe which causes dot based on which Egi is out.
Ifrit Egi - cast a fire burst aoe which causes burning for 20s on four enemies
Titan Egi -cast a earthquake aoe that causes heavy for 20s on four enemies
Garuda Egi - cast a tornado aoe which causes wind burn for 20s on four enemies
Leviathan Egi -cast Tidal wave Aoe which stuns up to four enemies for 20s
This would incorporate the Egis element and make them more unique.