1. Jobs are designed to specialize any given class. SE will never make PGL (or any class for that matter) a "super" THF, RDM, and MNK all in one. Its very possible it will have independent THF RDM and MNK(confirmed) jobs but it won't be, as said above, an "overpowered" superclass.

2. Most of your post is already being addressed with the MNK job. The MP aspect of the class is an issue but it is an appropriate one, if PGL was able to remain under the effect of its Fist attacks indefinitely then the class would be very broken. MNK is going to introduce a weapon skill that combos from Sucker Punch which will help alleviate the MP worries somewhat.

3. Once we gain Fists of Wind with MNK, extra Fist attacks would be nice (and will probably appear over time with level cap increases) but are rather unnecessary. If you play PGL correctly (that is, equipping INT gear like SE suggested with the new stat rebalances) then you will notice a dramatic boost in damage on the proper enemies. Doing 5-star GC leves I am usually pitted against Ice Wind Fire and Lightning elementals. All of which are lv52 and I have 302 INT.

Bare handed damage - 70~80 against all of them
Fists of Fire against Ice Elementals is the most prominent boost and each strike does 170~190 damage with 200+ crits. Against Wind and Fire elementals, I only do about 7~10 damage per hit :P and against all the other neutral elements I average about 100~130 depending on the elemental. Against those Fire and Wind elementals I usually change to Fists of Earth and put out that 100~120 damage again and I usually can get 150~170 damage per hit against the Lightning Elementals. (Fists of Earth doesn't grant the same attack bonus that Fists of Fire does) Changing from elementals to normal lv52 monsters, just subtract about 20~50 damage from all of the above numbers.

My highest damage on a lv52 Ice Elemental with Fists of Fire and a Combo'd Howling Fist with Blindside was 2305 damage. The elemental fist attacks work just fine, they just need to be used properly. While Fists of Wind will be undeniably useful against Ifrit (course, there will be a new primal by then, thanks SE >:| Can't yet us PGL's shine? ; ; Hopefully its Shiva so we can ra... do terrible things to her) it won't be absolutely necessary. Like I said, Fists of Fire works against anything that isn't Fire or Wind based, Fists of Earth takes care of anything that is.