I reread the PHB on Rituals last night, and thought about it some more. First, I am not sure Martial Characters really need Rituals. Of all the character classes, Martial Characters currently have the most options, so why do they need more?
Second, if Martial Ritual essentially becomes a variable feat, that is, you pick the effect you need right now, then it probably becomes the best martial feat, which is probably not what you want.
Third, it must cost something, otherwise characters will simply mash the Martial Ritual button every chance they get. So at the very least, you have to eat so many GP of Residium to power the ritual ("Just a teaspoon o' residium makes the meditation go down...").
Fourth, it must key off a skill. I recommend Endurance, the question being, can you keep up your katas or whatever for however long it takes to complete the ritual.
Finally, looking at the structure of the existing rituals, you can mostly classify them into ten minute and one hour casting times. My advice would be that ten minute rituals granted you a single use of a Daily Power that once activated would be in effect until the end of the current encounter, while hour rituals would be in effect until you took an extended rest.
If Martial Rituals are cheap and better than a good feat, they are broken.
Smeelbo
I'm not sure martial characters NEED rituals either. It was a topic of discussion and its always fun to consider what the possibilities are. It might add a bit to the game, but truthfully the options available in the core rules to all classes are pretty wide ranging already. MP adds some interesting builds and class features, but the core classes are pretty well set as is.
My proposal was intended to address the 'variable feat' concept in such a way that the result is a bit of flexibility at the cost of providing a reduced capability. If the various effects which can be accessed via this mechanism are fairly weak, then it becomes a reasonable trade off. The character can retool a bit between extended rests, but a dedicated feat would produce a stronger effect. Thus the ritual based effects MIGHT displace one or two of the more specialized feats, but probably still only for certain classes and builds.
I think monetary costing in general is a questionable game mechanic. Frankly I find the whole 'residuum' mechanic to be rather awkward and hokey myself. Inevitably players don't keep careful track of these sorts of things and it causes endless headaches or else devolves down into 'well, basically it doesn't cost enough to bother with'. A very high ritual casting cost may be pretty effective, but even then it is an awkward mechanic. If the GM needs the characters to be able to do something he's got to then come up with a plot device to avoid paying for it, and if he doesn't want them to do it AT ALL, then the ritual simply shouldn't be available. Basically a rule mechanic should be balanced within the framework of its utilization and cost should be relegated to the meta game where it becomes a campaign specific thing. So overall gold piece style costs to me are not a way to balance out game mechanics.
I don't see why it HAS to 'key off a skill', it can, and thats fine, but I don't know of a reason why that is absolutely necessary. I suppose an Endurance skill check requirement would work. It seems to be an undervalued skill in general anyway. Obviously it also reduces the overall value of the whole feature as well, since the ritual might fail on any given day.
As I structured it these things would give you access to some 'effect', and the suggested type of effect would be access to a special power. This power would generally be a daily (but could be encounter or even at-will in theory). This pretty much automatically puts the effects at a level well below standard feats, which mostly are 'always on' effects. The character would have the effect available until an extended rest/24 hours. If it isn't used within that time then the ritual has to be performed again.
At higher levels the available effects could be somewhat more extensive, so a paragon level ritual might grant a very minor at-will or continuous effect, or a daily use 'lasts till end of encounter' effect. At epic level the effects might be about on a par with standard heroic tier feats.
Obviously if they are better than a good feat then they aren't balanced. As I said, cost to me is not a balancing mechanic, but at least in the variation I suggested I THINK they would be weaker than a feat. It would really be up to GMs to insure that whatever specific rituals they added were balanced. Another consideration is that the whole feat itself might become too good if a LARGE number of these rituals were available to a specific character.
Overall my feeling is not to bother with the whole thing, but it could be an interesting mechanic for a specific variant class to be built around.