Alright, so I've been brainballing an idea for a week or so. Kind of different from what you'd really expect from a forum game, given that it'd lend itself to... literally no roleplay. On the other hand, it wouldn't really be a lot of dice rolling. Which kind of makes me wonder why I'd even think of running it as a forum game, but I think it could work. S'anyway, the idea was inspired from a handful of other games and ideas.
First thing that inspired it is the Action-RPG genre (specifically Diablo, Torchlight, Path of Exile, et cetera.) Mowing down dozens of enemies without thinking, just throwing down in the thicket as if the enemy doesn't matter. I've always enjoyed that idea; slaughtering mooks weaker than you. Unfortunately, forum as an environment doesn't lend itself to that, instead pitting the players against reasonably challenging encounters that aren't too different in numbers. The primary proponent to what I believe prevents this is a proper way of conveying the surroundings to the players, but that wall has been knocked down several times by several people and proves that even simple illustrated depiction can go a long way. This is, unfortunately, the biggest wall for me; I have no artistic talent whatsoever, no familiarity with any art program at all, and no idea where to start on making this happen (other than making pixel creatures because pixel art is comparatively easy.)
The second thing that inspired it is the ISGs ran here; a great deal of variety in setting, although the setting for this idea would be necessarily limited (would need a simple "automatic enemy" to fight against, and "automatic allies" to shop from.) Surrounding that, the story could easily be expansive, with many sidequests to do and zones to explore. Anyway, what I get from ISGs have been mostly from Evil Lincoln's games; a top-down view, with a lot of minions running around doing things. Changing the minions to enemies and having a focal hero would be quite simple, just using Evil Lincoln's games as examples; almost all of the work would be in terrain and the hero's "animation" pictures.
The third inspiration was actually the hollows of my own mind. I enjoy level progression. I enjoy it too much, in fact. So I want to stick leveling up into everything. The character, the character's title, the character's class, the character's equipment, the character's skills, the character's reputation, the zones, the bosses, the towns, the NPCs. Everything. With that as the final preface, here's a rough sketch of what I mean:
Adrian, the Underdog, Boxer.
Adrian gains stat points on level up. These stat points only affect his attributes (which would be simplified into Strength, Dexterity, Constitution, and Spirit.) The attribute points will mostly only affect his likelihood of hitting, his likelihood of dodging, his physical damage, his health pool and his energy pool. Seeing as I said we'd be reducing dice rolls, the hit chance would just reduce his actual damage by the chance he has to miss. Similarly, his dodge chance would reduce the actual damage he takes. In an ISG format, this is going to be basically the same as what he'd do anyway, as if we extrapolate the number of attacks he makes over time, it should effectively end up in a damage rate equal to just reducing the damage by the chance to miss.
the Underdog. This is his title. Titles should gain some minor bonuses that grow when increasing in levels, with perhaps higher levels gaining very low amounts of new bonuses. A fairly minor effect, seemingly unnoticeable throughout the game, but providing real bonuses. For the Underdog in particular, the title should grant bonus damage, hit chance, and dodge while at least 5 enemies are nearby. Since that would be all the time, except versus certain bosses (or maybe none at all!), the title itself would be useful for most of the game.
Boxer. As the class, this should have the most fundamental passive effects. Yes, passive effects, not skills. With the class, I'd introduce a passive ability tree, allowing players to pick how the class plays out for them. Perhaps one of the passive abilities sections would have chances for an additional attack whenever Adrian attacks. Maybe another section would be gaining a defensive buff every time he's hit. Maybe the class itself would have better single target damage, but less efficient versus large numbers, making his title his main tool for dealing with groups but a killer for bosses. This could be portrayed as "50% fewer attacks per round, but every attack increases your attacks per round by 1%. This buff is removed whenever the Boxer changes target." In 50 attacks, you're hitting more often than normal, and that is unlikely to take much time to reach.
Then we'd cover Adrian's skills. He can choose a skill every 5 character levels, but his choices are extremely limited (at least seemingly); he'd be able to select Strike, Dash, Guard, Orb, and Summon, for example. As a Boxer, he's particular about hitting things in close range, so he chooses Strike. At fifth level he chooses Guard. What these do at the start is very limited; Strike is just a double strength attack, useable once every two seconds or so. When the skill levels up, he can choose a few different categories to morph the skill, randomly selected from a list; in this instance, he could have Pyro, Cryo, Rapid, and Debuff. Pyro and Cryo would be related to dealing damage from those two elements (fire and cold), with effects "Deal 2-5 Cold Damage," "Deal 3-5 Fire Damage in an area," "Enemy is set on fire, dealing 2-4 Fire Damage per second." Rapid would be related to increasing his attack speed and move speed after using the ability, or closing the distance on the enemy, or generally just speed related effects. Debuff could have a tree for adding Stun duration to the ability, as well as reducing the target's defence, hit chance, and so on and so forth.
His equipment could gain levels too, gaining Diablo 2-esque Prefixes and Suffixes (and a randomized name after 3 or 4 -fixes.) What I mean by this is weapons can gain -fixes that add differing kinds of damage, lifesteal, manasteal, bonus to hit, debuffs, and so on and so forth. Armor would gain greater defence, damage block, damage return, resistances, and so on and so forth. Of course, why stop at just equipment gaining levels? Let's go ham, and give equipment sockets, and then make randomized items that gain levels (until they're used) that can be inserted into sockets. Because ham is delicious.
Leveling zones would increase the chances of unique monsters appearing and general rewards (which would be a lot of work for the GM). It would have some effect on the strength of the zone's minions, but a very low one. Leveling bosses would be similarly improved, and offer greater rewards. Leveling towns would mean more quests and better defences (so if a zone periodically attacks the town, leveling the town would make guarding it unnecessary.) Leveling NPCs (such as hirelings) would make them stronger, although they'd never gain the same benefits from a level that the player would.