One way that we limit summoners in our group is to have customized summoning lists for them. These usually represent fewer options that have been tied to a particular theme (I've put together 22 themed summoning lists as generic options), and tend to have much fewer creatures with their own SLA's.
For Skull n' Shackles, one of our players will be running a Master Summoner who wants to specialize in the elementals with a strong lean towards air and water, as well as the kinds of creatures one might encounter undersea, in the air or along the coasts. This is what we've come up with:
SM I
Dire Rat*
Dolphin*
Sea Shrike (Eagle)*
Stingray*
Stirge*
Viper*
SM II
Elemental, Small
Manta Ray*
Reefclaw*
Squid*
Sea Snake*
SM III
Crab, Giant*
Electric Eel*
Mephit (any)
Shark*
Thoqqua
SM IV
Eagle, Giant*
Elemental, Medium
Devilfish*
Sandman
Shark, Great White*
SM V
Belker (A)
Elemental, Large
Moray Eel, Giant*
Salamander
Sea Drake*
SM VI
Elemental, Huge
Invisible Stalker
Mihstu
Sea Snake, Giant*
Shark-Eating Crab*
SM VII
Elemental, Greater
Invisible Stalker (Advanced)
Roc*
Squid, Giant*
Dire Shark*
SM VIII
Elemental, Elder
Roc* (Giant)
Sea Serpent*
Sapphire Jellyfish*
SM IX
Shipwrecker Crab*
Great White Whale*
All of the 'normal' Elementals will be available, though not the odd ones like Time or Gravity. Same with Mephits.
I was curious as to what you guys might think of its balance (or potential lack thereof). I'd also really like to add a third creature to the SM IX list, particularly something aerial, but I'm struggling to come up with something appropriate.
Anyone? Anything?
It seems thematic but honestly I don't think I can help. I don't use summoning in my games as I feel it ends up with the GM fighting themselves. So I really don't have any meaningful input other than they look to be on CR for their caster level and they all seem fun and thematic for the setting. I do like skull and shackles and just that part of golarion in general.
Sorry no one posted on your post. I get the feeling. Sometimes I guess people just don't have anything to contribute?
It may be helpful to give people built in links to each of these creatures online? So they don't have to look it up to judge
One thing I see is your modified lists are short on the utility you can get with a summoned monster if you can communicate with them. As a summoner in Skull and Shackles, once I was able to get to Summon Monster VI, I was able to summon erinyes devils, not so much for their combat prowess, but because they had true seeing.
If there's anything wrong with the summoner (other than eidolon building rules that are way too forgiving for power builds for the original version of the summoner) is that they're long on close combat, short on utility. And, as I see it, the ability to summon creatures for more than just combat is one of the best parts of the monster summoning magic - whether cast as a spell or as the summoner's SLA.