I agree with Tharluk, It's fine if you were in a zerg filled with level 40 characters filling your ranks, but if you're trying to solo or as soon as you meet a premade/gank group, the skill, and tactic differences alone between a level 40 player and a T2-mid T3 character are pretty big.
Also, this is just me but as a level 40 it's a bit tedious to have to go back to T2, and T3 just so I can play on T4. (Though I see what the event is trying to achieve) In my opinion, it negates the rewards for trying to reach end-game too since there are some of us who try to reach 32+ just so we can play in the Tier 4 zones.
Enemies will have level 17+ characters too that's true, but since T4 is the most populated, and since they all have to play in T2, and 3, just to go back to their own zones I need to guess which 1 character out of that group isn't level 40, or doesn't know how to play use his own class in order to get a kill on my own. To me it's one of the things that made Age of Reckoning's RVR unique and enjoyable, any zone I went to at any level I at least had a big chance to kill anyone on my own without having to rely on people with higher levels than me.
This game has stealth classes, and plenty suited for fast escapes fighting solo will be unavoidable in most cases (due to Ganking). Though this does exist in higher Tiers like I said with the Skill, and tactics differences etc the difficulty would be amplified. Let's say your group is far and at the enemy castle on siege no time to go back for your level 20 char, depending on the map you would be stuck in that camp until someone decides to come back.
Became a bit more zerg centric too In my opinion pop differences are amplified as compared to before, not to mention from time to time too laggy to be playable since I'm connecting from south east asia. (as soon as we hit 3 warbands, this happened too frequently)
Do think this feature should be kept just for events though.
Just my criticism I won't hate, nor stop playing the game if this gets implemented fully.