Searchers of the Unknown is a great concept for a lite game. Characters use a OSR D&Dish stat block, just like the monsters. The original SOTU rules define only fighters, so it offers limited options for characters. Basically, you can be either a Fighter or a Thief. This limitation allows for a tightly focused ruleset for the roles required in the game. Magic is implied to be a scroll, potion, ring, or miscellaneous magic item type of thing. The rules state very early on that Clerics and Wizards do not go delving in dungeons.
Like many mini-RPGs, add-ons and expansions began appearing all over the net. Some changed the ruleset to Target20 and D20, some added spell casters, and others changed genres. You can get a collection of these expansions on Randall's website here. Just like Microlite20 Legacy, a small ruleset begs for filling in perceived gaps. I am not immune to this desire.
When I look back on the history of D&D, the rationale for the creature stat block was partly to conserve space. A bigger reason, though, was that monsters function differently from characters. Up until 3e, characters had stats, but creatures did not. Making monsters was an entirely different process from creating characters. For SOTU, this means that there is a shift away from this separation. Creating characters is a lot more similar to creating monsters.
Looking at character creation this way, how do you create characters with different abilities without importing rules from the players' sections of d20 or OSR games? SOTU is based on D&D, but it is a different game with different mechanics. The biggest change comes in determining success with stunts. In exploring SOTU, I'm going to add-in special abilities like Turning Undead, Potion Creation, and more into the stunts rules. Part of the appeal of the original game is that characters can do just about anything but cast spells. I aim to change that as little as possible. The obvious exception is that I'm going to provide a way for spell casters to escape their cloisters or laboratories and get into dungeons.
It's easy to say something is missing from SOTU. Like I said earlier, its size invites house rules and sub-systems. However, in any stat block from D&D based games, many monsters have something equivalent to a Special field that demonstrates some ability that is different from just the listed attack. For example, medusae can turn others to stone, dragons have breath weapons, mummies have a rotting disease, etc. Monsters of the Unknown (part of the collection mentioned earlier) adds a sentence below certain creatures to represent special abilities. For now, I'm just going to add a field with a three or four word description of that power instead of a small paragraph below the stat block. In other words, I'm adding a stat to the block.
So how do we know what the special ability does? The different supplements offer contradictions with each other (and the SOTU core document) about various abilities. Spells in SOTU have limited choices for range (one dungeon room), area of effect (one dungeon room or 1 person per caster level), and duration (one fight or one day). Other supplements, however, provide range in feet, duration in various units of time, and other variations. Mutant Scavengers of the Ruined Earth, however, offers 20 special abilities, called mutations, with effects defined within the constraints of the original rules. Starting with these 20 special abilities, it should be possible to offer spells in the same way. Coming up with powers, though, will likely require a second page with "reference" information. Maybe I can shrink it down.
Here's the bottom line: SOTU is a very interesting experiment. I plan on playing with it to see what I can invent. I want to add spell casters, but beyond that, I think it is possible to add a variety of player abilities without expanding the rules with a bunch of sub-systems. I also want to stay as close as possible to the original rules. Why? SOTU really is a different game from D&D or Swords & Wizardry. It is not a straight clone and the mechanics for certain things are quite different. I want to see if it is possible to create different games and supplements for it. Don't get me wrong, the existing add-ons are great. I may not be able to write anything nearly as good, but all the fun is in the making, right?