Reached level 20 (Rank 5) yesterday and I don't want to buy any new abilities unless you can get more level credits, does anyone know if you can, and if so, how? Thanks

Capped at level 20.

if you want to change any of your abilities, you need to use the "sell all" option to reset your abilities - that drops you by one level, so you'll be at level 19. You can also create a new character (up to 10), and create a new setup that way.

But once you reach 20, no more credits, and no more abilities.

Kinda makes the Rank 5 Unlockables useless =( whats the point in spending 1 point in say the Engi class for the Gatling turret... when the level cap is 20 and nothing is earned for it.

Starting again with a fresh character obviously locks those types of equipment until rank 5 is reached again. I can only hope for a increased level cap so i can earn some points with the later unlocked items.

Not quite sure what you're trying to say with the first sentence. Do you mean getting multiple Rank 5 skills? If thats the case you can just save a skill point when you hit 19 so you have 2 available at 20.

That's the absolute point of it,So that people can focus on one class.

My main character is mostly engineer,but I have a few operative skills as well,but when I hit level 20,I went for the Gatling turret instead of any of the other rank 5 skills.

They made it that way for balance.If you could get everything that you wanted,then it would be totally OP.Simple as that.

Pretty sure he's actually saying that he's annoyed the extra XP he earns with the gatling turret doesn't go anywhere, actually...

It does though, especially in Stopwatch mode (which really is the only viable competitive option). If both teams stall one another on defense at the same stage in the mission, the match is decided by XP.

Also, it determines who gets rated "best" in their class and overall.