Functionally, I'd do something like a world where magical powers are incredibly rare and those who posses and can naturally access them are far and few between. These people are born to be kings.
However, the most powerful of their abilities is that they can infuse others with their own energy, unlocking their abilities and allowing them to fight with unrivaled strength. Thus it is that these casters assemble retinues of powerful servants whom they imbue with their powers and then send out do battle for them.
Unfortunately, the inborn potential of many, while immense, is locked deep within them and can only be unlocked with an immense expenditure of power, blah, blah, etc, etc, hence justifying the sliding scale. Unlocking these powers takes minimal effort, although there is a limit to how thin a mage can stretch themselves. Thus, any mage without a cohort is at a huge disadvantage, as they themselves always maintain about the same power level, even with their max cohorts.
Lot of different ways you can go with that generalized set-up. Story of a heroic underdog, story of a fallen kingdom, story of a tyrant overthrown, story of selfish dude just dicking around, story of love, story of friendship, story of classism, etc, etc, etc. It generally lends itself towards SRPG style in concept which is annoying, but it is fairly easy to avert by making them small scale conflicts since even the most powerful mages can only infuse a handful of individuals at a time.
A summoner style game trends a little bit more towards generics, and that's back into SRPG territory. Also, generics are lame.
Generally speaking, the biggest challenge would be characters. As we found during the last project (which, even more importantly, was purely theoretical), large casts are a mothereffer to handle. Moreso if you want it to be a story game. Learning from the last project, I'd say its doable and we could manage a pretty good cast size (let'ss say... what? 1 Summoner/Master + 3 cohorts max to the party, Summoner being locked... hm, 21-24 characters spread through a few tiers (4-6) sounds like a decent number. Create a set of core characters (Summoner + 4-5) who the story really revolves around while the others are more side oriented and it... might manageable?
On second thought. The other big risk is a problem with really utilizing the concept. To actually do it, I think you need split part sections, which throws plotty stuff into weird places unless you maybe have an allied mage or two? You might also want to step the mage back into a non-combat role (i.e. not present on the field and have his influence represented by buffs available to the characters or something?)
I'm totally rambling now.
Story-wise, it isn't too hard a concept to go up to bat for. Gameplay-wise I struggle a bit, however, to find too much benefit outside of a full SRPG style set-up. I guess the question is how do you really justify the stratification of characters like this in a meaningful way? I mean, you can always do it just because or because you like it stylistically (s'cool to do things you like) but... well. To a degree, I guess the issue is how much do you gain?
Nyarlie's actually tends to run towards the logical route, which is maxing the PC count (or running one short to maximize the number of high tier characters you get), right? I guess maybe you could categorize it up a different way if you want the gameplay to focus around weird synergies...
Ah. That's it! Yus. Better story justification! These inborn powers are all tied to one of the elements. Mages possess souls attuned to all however many elements, so they can attune to the person to let out all their power. However, they can only attune to one person of particular element, zodiac sign, whatever at a time normally. Thus you stratify your characters across thematic concepts rather than raw power or something, or you could do it that way and just tier the elements, metal> fire > earth > water > air > wood and make the concept a little less meta.
If we were aiming for a shorter game, you could actually like perma limit such things and remove choices throughout the game (you assemble a permanent party over the course of the game, culling useless choices/getting them killed/etc) and have plots vary along those lines or just do Suikoden style ALL OF THE DUDES kind of play.
Actually, going way back? I like the idea of the summoner not being present on the front line most of the time. Thematically, that raises up a lot more fun questions about morality, friendship, intimacy, etc. Are these people tools and slaves, or are they people you care about? Maybe give attuning this whole mental connection thing and explore what it is like sending those people out to die.
Even doing away with the point system (which we don't need to do, just saying) the concept has merit as a story to be told.
Hrm. You could also go another way and maybe use the characters as avatars as well. You don't just send them to battle, you unlock some totemic dealy within your soul and transform them into beasts/monsters before sending them out. Totally do a darker/serious exploration of the core pokemon concept, as well as looking at the dehumanization (literally) of your comrades as your exploit them and use them in battle. It is something to unlock powers in them and have them fight, it is another to release that horrific dragon in their soul and have them eat people.
I apologize if none of this made sense. I did this in like, 10 edits because new thoughts kept occurring.
Son of a bitch. This is like my 30th edit. Actually, more and more I like the idea of more full control of unlocking terrible things from inside people's soul because this totally gives opportunity to start the main off as a completely terrible human being and evolve him along that line. Watch it finally start to effect him as he realizes that, yes, these changes over time have horrible effects on people.
Oh man, this totally lends to some awesome potential for branching paths and legitimate moral choices.
