Guild Wars 2

Allow a double up on a trait line;

Players could choose to completely forego a third trait line in order to select a second trait from each tier of an already selected trait line.

For example;
Beastmaster
Beastmaster
Third trait line forfeit

No, this would result in stupidly unbalanced builds. Also just the thought of double beastmaster makes me shudder.

PvP is not balanced at the best of times, this would really brake things.