Pretty much everyone said something along these lines already, but since I played SMN from 2.0 all the way until switching to PCT with 7.0, I feel like I need to just...restate them all again, I guess.
The problem isn't with the rework in 6.0, it's that they claimed the reason for the complete overhaul was to give it more room to grow in future expansions, then proceeded to add absolutely nothing to it in 7.0 but another Bahamut. At the time of the rework, I was very happy to finally be rid of Summoner just being a Warlock from WoW, and I still think it's more like a Summoner should be than it was the whole time leading up to that. The main issues it had at that time - not as many actions, still just the same five summons they had before, Carbuncle just kind of being there and not doing anything - all still exist after 7.0 despite many things they could have done to fill in the gaps.
Like a lot of other people, I think the easiest thing, maybe even the "bare minimum" now, would be to put the other three elemental summons in and have them rotate along with Bahamut and Phoenix according to their aspects (Ifrit/Garuda/Ramuh after Phoenix, Titan/Leviathan/Shiva after Bahamut). If they really want to keep the other "demi" summon, I think it should have been another higher-tier one instead of a Bahamut reskin, and then they could either give access to any three of the other six after it, or add another set to go after it. Additionally, they should have fixed the fact that Summoner has very few actions by adding more that change along with every summon or possibly more oGCDs that are tied to Carbuncle instead of just having them come directly from the PC.
SMN and BLM right now have the same problems for me - they're less fun versions of RDM and PCT, jobs that actually get to cast spells of all the traditional elements and match up to what people expect from them in a Final Fantasy game.