This is NOT a tradeoff idea. It's for ALL mesmer elite specializations, as well as the core.
Here's an idea.
I guess it's obvious that portal was a very strong utility skill, and it was mandatory in high level play so it was nerfed. What I have in mind is to make portal a class mechanic for Mesmer, including elite specializations.
Portal should be F5 and it should not be a shatter nor a glamour: so it's not affected by Signet of Illusions. It also shouldn't be affected by Continuum Split.
Of course the current utility portal should be removed.
This is the skill:
Portal Entre (50 second or less cooldown)
Creates a portal for 15 (or 20) seconds at the mesmer's current position.
Creates the other portal.
Maximum number of players who can pass is 3 in PvP and 5 otherwise.
Stays active for 15 seconds.
There should be a trait in illusions or domination (so in a damage-oriented specialization) like this:
Extends the time between portals from 15 (or 20) to 25 (or 30)
Extends the number of players from 5 (3 in pvp) to 10 (5 in pvp).
No cooldown reduction.
The reason I thought of this is to add another playstyle to Mesmer: A rotational damage dealer (like power herald) in pvp. It will also help fractals and raids too.