I'm not saying this to be a jerk, but are you new to RM?
The reason you go through all that character generation process with all those stats, is for when these problems come up. If the GM feels those skills are needed, you chose the primary stats to assign to get the bonus. Add professional bonuses, and professional cost, and boom you have a new skill. Problem solved.
Also talent law has things that add these types of abilities you are asking for.
So answering these is redundant but easy enough. As your gm could simply add any skill he deemed is necessary.
"Fumble not tied to competence of combatants."
Fumble is a luck thing and is tied to your type of weapon. 2 handed weapons have a larger fumble range. The swashbuckling skills work on this, and you could simply add a anti fumble skill akin too the disarming skills. If you feel it was that necessary.
"Critics are too random. An "A" critical can kill you with a bit of luck. (I like realism, but dispatching PC randomly isn't a good choice)
Too simple to kill very impressive monster, doing super-roll."
Crits are luck. If you don't like that Add Fate points from the (RMSS Channeling companion), these are added like 1 per game for intense combat, maybe 1 per level for less combat. These emergency points save characters from insta kills like that. And most GM's fudge those murderous rolls. Also super monsters have super abilities. Undead's stats seem weak. But if you add the stat drain, the group is in big trouble unless they have a cleric (as if their Constitution reach zero, they become lvl 1 created undead).
"No locational damage."
Did locational damage in Palladim. Sounded great was not so good in practice. But there is a skill that allows one to adjust crits up and down (rogues use it alot). If combined with a talent to do it from any postion, it becomes very powerful. A rogue crits you and adjust the crit up or down for each rank (not skill total) they have. And of course they adjust it towards the nastiest crit. I believe rogues get it the cheapest, but combat types get it cheap enough. If not you can add a skill and everyone in your game will just hit the guy in the eye, groin, head, or whatever.
"No dodge."
This is probably on purpose. If you use anticipations this subtracts 50 from the attack, and is instaneous (as long as the person can see the attack coming). This spell can be powerful (so if you have a caster there is that to add to dodge). There are also the adrenial moves and such (usually associated with martial artist) which adds to the DB and OB etc, which is considered over powered by our group (but would be logical if your using a martial artist). Warrior types are fairly good at doing this.
"No shield skill, only a flat bonus."
20 points, plus a quality shield, quickness bonus, racial bonus (caster casting blur,shield( if they are using a shield), anticipations etc). You have a huge bonus. Then if you use Talent law they can do even more to it, you can end up with some crazy Defensive bonus's. Again add Adrenial skills and it can be absurd, but that is up to you.
"RMC presents rules for breakage insanely complex (how do they worked out them... )"
The weapon breakage rules are simple (at least in RMSS) it's on the weapon chart. It is the thing called weapon breakage #. If you roll the doubles listed on your chart you have to roll to see if you break your weapon. Add your weapon strength, weapon quality and then make the roll. If it gets over a certain number, the weapon has reached it's breaking point, snap. Weapon gone. If the GM wants you can have a person roll the same breakage number any time it seems appropriate.
"No defense roll. Instead of putting a bonus in defense I'd like an active defense. This way combat is more dynamic (a double fumble!!!! )"
I'm not seeing the double fumble coming out of this idea. But again if you want an "active" defense add adrenial moves. It will be more absurd than Shadowrun, rolling 30 die for defense, but it can be done. And Rolemaster already has critical fumbles (which is essentially a double fumble). If they roll really bad on the fumble they can practically kill themselves. In fact we had an arcanist fumble so bad he killed the entire group.
"Weapons table are diverse but similar. Doing an "E" critical to a naked warrior with a dagger is the some sa doing an "E" critical with a Great Lance at full gallop wiht a Heavy Barded, Heavy War Horse . Difference is hits, but not too much. This change, a little, with higher AT20, but depends on the weapons.
Etc."
If you use the rules for charging there is alot more damage. And heavily armored people are much easier to hit, but harder to crit on. A person not wearing armor is harder to hit, but easier to crit on. So your dodge rules are already implimented. And damage is damage, how much different do you expect the damage to be from one E to another E? If one type was too unbalancing, then everyone in your game system would use that same type of weapon to attack (the first time our group had void bolts came to mind). I'm not sure on your meaning of the barded horse? A heavy War Horse would probably charge faster without the barding, but would be heavier (and thus slower without the barding). Mass x accelartion = power. If you lose the speed you lose some attack power, but if you lose some mass you lose some power. So from the charts point of view it is easier to have one simple answer. Instead of 600 for each situation.
As one of my teachers used to say "there is no such thing as deader". An E crit on one guy may be described slightly different, but in the end dead is dead. And watch out for those A tiny's , we had a group lose many eyes from a group of styrges... It was so bad the GM had to say, you wake up at the Inn and strangely you all had the same dream...We now fear A tiny criticals as a group....heh.
But the RM system in my experience already has the answer to most of your questions. It's just usually we are looking in the wrong place for the answers
