This is just my oppinion and I am sure many people will think I am wrong, but here goes. The Pale Master class is not as over powerful as everybody makes it out to be, at least not when it is mixed with caster classes. PM's do get an increase to the spells per day(evey other lvl.), but they don't get an increase to there caster lvl. and the do not get new spells.(only really a problem for sorc and bard). This means if you only take 3 lvls in the class you choose to qualify for it, you will be doomed to cast all your spells at 3rd lvl effect(3d6 fireballs, yippie). Pm's also get the worst base attack and only slightly better hit points then your average rogue. And for this they get imminity to crits and really good natural armor bonus. For a caster type this is not over powering, it is an edge to stay alive long enough to get your spells off( very important on servers with dev crit ). So it seems to me the real problem stems from people making uber melee builds mixed with 3 lvls in something and then 10 in PM. Now I personally still dont see this as problem, but I can understand how other people could. I quess my thought is this, if there is going to be a restriction on the PM/figthers, then make the restriction that you can't take warrior classes with pm. After all you would think someone who has mastered the arts of nercomancy wouldnt have time or the interest to persue a fighters carrier.
If this is the type of build I wanted to eliminate think i would instead make the restriction: You can only have 4 lvls of a base melee class(any with fighters base attack,not including prestige class, making the base attack requirement for them will keep you from getting to many attacks), and still take the PM class. You must still take you first PM lvl at 20th or before.
The you could unrestrist the bard and it would become the only good tank style PM, and if my math is right you still couldn't get 4 attack/rnd( let me now if I am wrong.)
I would like to see a new method, mostly because unlike some I dont feel bards shouldnt be allowed to become PM's. I have used many undead bards in my PnP games and they are always a blast.
Oh well I ve ranted long enough, just my 2 cents..