My biggest problem with the SR4 mechanics was speed. It took too long to run combat. To attack someone you calculate your die pool (remember that recoil, folks), then roll your attack and count up your successes. Your target then gets a free defensive roll, and after he generates his successes, you compare results and cancel one another out. If you have any successes left over, you hit and your opponent then makes a soak roll. Finally, he records damage and you move to the next person in the round.
Now, there are ways to speed this up. Rolling simultaneously, for example, does cut down on the time a little. But SR4 die pools are large, and it takes a short while to sort out your results on a roll. Individually it's not a big deal, and this is why it wasn't a problem at first. But eventually the entire thing begins to drag. Multiple opposed rolls that use big die pools was something I couldn't get over.
I had previously attempted to port the game over to Feng Shui, but while it was fast, even modified it didn't feel like Shadowrun. It didn't find any traction with my players. I also tried using the One Roll Engine of Wild Talents, and while this worked reasonably well, there was a problem in that I found I needed to individually craft every piece of cyberware, every adept power, and every spell. The game is a super hero game, so it had everything I needed to do this, but it prevented the players from feeling like they had control over their own characters. I like both games quite a bit, but for Shadowrun, the dice weren't right.
I think the best way to approach the system is to do something similar to the setting exercise for the rules themselves: create a list of essential elements that either must or must not be in the rules, except this time it's a strictly mechanical discussion. So for now, this is what I'm working with:
- Limit Die Pool Size - As noted above, one of the limiting factors I found in SR4 was the sheer number of dice everyone threw to perform actions. If you had an optimized character (and my group had several), you could be chucking close to 20 dice for an action. Even with simple resolution mechanics, that's a lot of dice to sort. In the interest of speed, I want to keep die pools small.
- Limit Die Resolution Complexity - This was something I think SR4 and nWoD both do right: they make reading your dice easy. Roll a die, look for a number. If you got that number on a die, it's a success. Thing is, the number is the same every time. In Shadowrun, if you roll a 5 or 6 on a die, it's a success. Difficulty is set by the number of successes you need, not by the number you need on any particular die. That reduces the amount of math required in resolving your action, and that makes things go faster.
- Minimize Opposed Rolls - Opposed rolls require two people to roll and calculate their results, then compare them and perform some other calculation. Even if these things are simple, an opposed roll is inherently more complicated and takes longer than a static one. I'm not opposed to the idea of an opposed roll, and I can imagine a number of situations where they are the most logical way of resolving a situation, but I don't want them to become the default mechanic. I think a lot of situations in which other systems use opposed rolls can be resolved with rolls against static targets.
- Build in Gradient Success - Some systems use a binary success model: you succeed or you don't. Gradients means something about your roll says not only if you succeed or fail, but also by how much. This isn't anything new, but it's a very popular concept among my gaming crew, and it sits well with me as well. In fact, my group has asked me to include this in the system, specifically as it pertains to combat. They want the quality of the attack to modify damage, and perhaps to merge attack and damage rolls into a single toss of the dice, much as Shadowrun has done for decades.
- Speed - As I noted in the flavor elements, speed augmentation is important to the genre. Thus, there needs to be some kind of speed mechanic in the game. Some games, for example, forgo initiative and combat order in order to make the entire thing simpler and faster. Neat idea, but counter to my purposes in this game. A street sam with wired reflexes needs to be able to jump all over the slower opposition. At the same time, the advantage can't be overwhelming. This is a game, after all, and the guy playing the mage begged me not to leave those unable to get cyberware out in the cold as happened in some older editions of the game.
- Wound Penalties - This is an old staple of many, many games, but there are a few reasons I want to include these beyond precedent. First and foremost, Shadowrun is a game about supernormal characters, and I don't want to lose sight of the normal part. Even highly skilled people take a ding in their performance when they've been shot through the leg. Plus, wound penalties provide something else cyberware can mitigate, creating another use for the implants and ensuring greater variety of available enhancements.
- No Death Spiral - We've all been there: you're in a fight and your character's not out, but he's so crippled by penalties that he's effectively useless. The best you can do is hope the fight ends soon. No fun at all. This means while I want things to become more difficult for the characters as they get hurt, I need to be careful that as long as they're active they're still capable of succeeding. However I represent damage penalties, be it increased target numbers or roll penalties, they need to stay within certain limits.