I think they should be given additional skills to give them a bit more utility, rather than removing them. Ifrit, for example, could grant Enfire to the party, adding additional fire damage to every attack. Garuda could grant a spell speed increase similar to Serene. Titan could grant a defense bonus. It'll never happen, since SE is forcing every job to be specialized rather than generalized, but it's the only way Summons will be more than just another tool.

Garuda is going to be the main summon for a very long time. Ifrit and Titan are already out of the runnings, so we'll have to see what Heavensward and the level 60 cap have planned for Summoner to see if Garuda is surpassed.