The grizzled veteran partnered with the new recruit...the master and their apprentice...the immortal wizard, the elf who has lived for centuries, the dwarf only slightly younger, and the hobbits barely out of their adolescence.
We've all encountered the stories where characters are not equals, yet it remains the default state of the table that everyone is "equal". I've certainly encountered long term games where characters are killed off, and then any new characters are introduced at base level. I'm similarly aware of campaign play in Ars Magica or Pendragon, where a single story can continue over the turning of decades and generations. But the default is still the "equal" party across most gaming. Personally, I think the potential dynamics of young and old characters offers an added level to a story.
I'm thinking of a system where characters start the game at various levels. Those who are young are still filled with dynamism and wonder, they may not have much experience, but they can quickly adapt and learn new things...those who are old have become set in their ways, alien in their thinking, and laden with ennui, they struggle to asassimilate new knowledge and techniques. In The Law we might be looking at the difference between a fresh academy graduate, and a veteran "with three days to retirement". In Familiar (or "the unnamed denizens of the Dark Places" project, which may or may not end up different), this might be the difference between a freshly spawned digital sprite and an ancient primordial entity who has maintained an aspect of fundamental reality since the dawn of time. Vampire: the Masquerade tried to do something like this in a few of the sourcebooks designed to address the "elders" of the setting. But the Vampire way of addressing the concept was messy and inelegant. One of the much discussed issues in Vampire (and all games in the Storyteller System) is the way element costs at character generation vary compared to the systems used in play to increase those elements, and then you've got freebie points that work in a different way again. This basically means you can create a character designed to be a "builder", who might seem sub-optimal at the start of play, but once experience points (XP) are added after a few games such a character can shoot ahead of everyone else in raw ability despite earning the same XP. The "Elder" addendum to which I'm referring just makes this more unbalanced by further modifying the XP expenditure and tacking on extra freebie points. But it kind of goes in the direction I need; I can see that it was aiming the right way, but didn't quite hit the mark for me.
I guess my biggest gripe with the system presented is the fact there are already two subsystems at play with a disconnect between them, and this tacks on a third subsystem without addressing the discrepancy between the first two.
The experience system in The Law is basically derived from Mordheim. It has a track of checkboxes, and some of those checkboxes are bold. Every time a bold checkbox is reached, a character gains an upgrade; but as the boxes are marked, tbose bold boxes get gradually further apart. Mordheim addresses the issue of asymmetrical power levels by simply giving the team leader higher stats, but automatically checking off 20 boxes... therefore instantly making future upgrades for tbe leader harder to achieve regularly. Team lieutenants have slightly upgraded stats, but check off 8 boxes. Another factor comes into play with various costs to recruit team members, but that makes sense for a skirmish miniatures game. The balance in Mordheim isn't perfect, but it's also aiming in the right direction for me. It also has the implicit idea that not all characters are expected to survive the session.
So I'm up in the air again.
I'm really tempted to use a semi-random allocation system again. Such a system might use d4, d6, and d8, with allocation categories including the number of XP checkboxes already marked off (and associated advantages gained), the number of special contacts and other advantages gained (which are usually acquired through roleplaying and narrative rather than mechanistic XP), and the final category would be the number of penalties a character has picked up over the years (which would be like the sacrifices in the regular game, where better rolls equal less problems). Such a system deliberately promotes differences in characters, while adding depth to tnose characters who do have a few stories in their background.
Still thinking though.