rank gain and restrictions.

[(TLL) Heretic]

*SNIP*

The steel deathtrapness of the mech is exhilarating too.   The most exciting target I've ever engaged was a Siege Engine.  Slapped it upside the face a couple times before the pilot decided I was worth the effort to shoot back at.  Promptly RTB'd after surviving the initial barrage of UAC's and dodging the first volley of ATMs, but my pocketbook was stuffed by the time I made it back to the hangar.

That sounds very familiar
*Eyeballs Armchair* 

A PPC Osiris pilot can actually force a Siege Engine to RTB if he's very good and the terrain is forgiving to the little guy.....odds are stacked heavily against him though...2 good PPC Osiris Pilots working together can be a very different story! 

[Spooky]

Not trying to be a jerk here, but ranks are based on score. If a late joiner does actually do more for the team (i.e scores more points) he will gain that rank bumping down whomever currently holds it.

that was different in the versions I played before. I guess they sneakily changed that in the newer versions.

/thread end

As Atlessa pointed out, it was already like that for a long time. However you are not promoted/demoted immediately. Maybe that's why you thought that it won't happen at all.