For level range, I think there's an awful lot to be said for having a soft cap on levels around the 10-12 mark. XP gain rates can be tailored so that by the time PCs are around these levels, progression is all but non existent. There are several reasons for this. From a design perspective, creating balanced, static content for high or epic levels is exceptionally difficult; creating said content in a world that also includes low and mid levels is even harder. Also, the power gap between high/epic and low levels is all-but unbridgeable. I think it is also preferable for PCs, when they into their mid-levels, to be focussed on 'story' and 'plot', i.e. playing a creative role within the PW, than their individual 'adventures'. Level 10 fighters should be guard captains or mercenary commanders; Level 10 wizards should be teaching PC apprentices; Level 10 clerics founding temples, and so forth. This kind of approach also feeds into my points about a player-driven world. By level 7 and higher, PCs can act themselves as quest-givers and move the world on, in the absence of DMs; this kind of activity, which has been terribly rare elsewhere, seems like one of the keys to a self-sustaining PW.

Cipher wrote:

I'm not fond of level limits, partly because I know that a lot of the fun of playing a game like D&D is in growing the character. It's nice to have pleateaus in the development, but I'm just not fond of a cap, either imposed as a hard limit or a gain limiter that makes it all but impossible to progress.

Having said that, I like ideas that promote player-to-player interaction. Ignoring the potential practical limitations of the idea for now, what do you think of awarding XP for levels beyond 12 solely through these kinds of interactions, such as apprenticeships, quest giving, and fulfilling other IC duties appropriate to characters of that level? The XP cap then works to its intended effect - encouraging interactions in a player driven world but without diminishing the player's interest in their character by prematurely ending its development.

Perhaps an XP system that means that, at higher levels, significant gain becomes DM & plot dependent. Essentially, a kind of soft cap - I'll reference CoA again here, as they - technically - go level 1 - 20, but levelling slows down seriously as PCs go through their mid levels and it is very rare that PCs get beyond 11 or 12. CoA seems to still have a plethora of PCs of levels 8-11, for whom progression is simply no longer an issue: they are tough enough to make it out of most dangerous situations if they want, they have the skills to do most of the things they want, and they can focus instead simply on story. And, of course, just because the engine goes 1 - 30, I'm not sure that means it has to be mimicked.

Also, in a permadeath setting, the level gap gets heavily accentuated if you have smooth progression. I recall my own PC (Elf Fighter 8 / WM 1 / Ranger 1) being/feeling absolutely pointless when partied with Alara's Fighter 14 DC 5 Wizard 1. The gap is just so huge that lower level PCs are almost entirely redundant - even when those PCs are themselves significantly powerful. High level PCs can take out entire armies, raze towns, end plots with a single strike, and so on - it's almost impossible to provide for in a true RP PW. For instance, if your villain is a local necromancer (let's say, Jim, a level 9 wizard) who is creating a secret undead army to overrun a village, and the main protagonists are a group of PCs of level 3-6, all's good and fair, but then Bob the Level 20 PC walks into town, and with a bat of his eyelashes annihilates Jim and his army. Bob's a LG Good Guy and it would be totally OOC for him to simply ignore Jim and his activities - but in order to make Jim proof against epic PCs him - and all other villains - have to become epic themselves. In the alternative, if there is a soft cap of 9-12 (i.e. things get real slow, advancement-wise), you know what the maximum 'random' power variables are and can adjust for them accordingly.

It's also incredibly hard to have static content for levels 1 - 20 without just having *portal to hell, pls go fight demons* and so forth.

And, of course, more generally, the d20 mechanics get seriously broken after the mid-levels, tho' the extent to which we adapt the GoO ruleset may have an impact on this.