Just checking: PMC=Player Multi Class? Sorry, but too many contractions out there for me to keep track of them all.
PMC = "
Paragon Multi Class". The option to miss out on a Paragon Path at level 11+ and take powers from your second class instead. Specifically:
- IF you take a total of FOUR feats (original MC feat plus Novice, Acolyte and Adept feats for encounter, daily and utility powers) you can PMC
- At 11th level you get to swap (not add) an At-Will from the secondary class in place of one from your original class; you also get to choose a 7th level Encounter power from your second class
- At 12th level you get a 10th level Utility power from your second class
- At 20th level you get a 19th level Daily power from your second class
No AP ability, no additional class features, no neat 16th level path feature - the words "second class" seem to me to be incredibly appropriate, in fact.
I understand the reticence to "give away" At-Wills, but a feat to give one as an "Encounter" ability that becomes fully "At-Will" upon PMCing does not seem unreasonable. You can only use one At-Will at a time, so adding them rather than swapping is not really that big a deal (as WotC realised later on).
In general, though, a feat tax per power to swap Encounters, Dailys and Utilities is extremely harsh, and a 4 feat requirement for a Paragon Path substitute that delivers sub-level powers and no features is completely unattractive. I think the designers were overreacting to the hopelessly overpowered multiclassing in 3.5 and never really revisited the system, substituting the rather dodgy "hybrid" rules for it instead.
After a bit of thought, I would keep to more or less what I said in my earlier post to this thread, but make the At-Will feat just as I described in this post. I would add in feats for class features for each class, with the more powerful ones taking two feats but with PMC counting as the first feat of each pair for the purposes of getting the second. For example:
- A feat with a prereq. of the Rogue MC feat allows sneak attack once per Encounter
- A second feat with the above feat as a prereq. allows sneak attack per round. PMC Rogue may count instead of the above feat as a prereq. for this feat.
At 11th level you get an ability when you expend an AP, generally an extra use (if already spent) of a class feature.
At 16th level you get an ability for use either when bloodied, when using s second wind or when reducing a foe to 0 hit points, generally a class-appropriate immediate boon.
At 11th level you get any additional Encounter power from either class (subject to the "no more than half of the powers in each category may be from the second class" which always applies). The power must be both at or below the character's level and at or below 13th level.
At 12th level you get a Utility power from either class of level equal to or less than both the character's level and 16th level, subject to the same conditions as the 11th level Encounter power.
At 20th level, you get a Daily power subject to conditions just as for the previous two, with the "level cap" being 22nd level.
That would need playtesting, but anyone who wants to try is welcome!

Please feed back here.
If I get inspired I might take a stab at the feats and 11th/16th level abilities for at least the "base" (PHB) classes.