Just my 2 cents for Dual boxing. I was an open beta to C4 player, and have spent far too much time in Lineage. I play the private server to have some of the fun i used to have for a portion of the time invested, but some of the concerns I've seen voiced here with being tough to find parties for tougher mobs due to lack of player base is pretty real. Having a dual client would open up some tougher leveling zones for those of us who play opposite the main server hours when it is tough to find groups. The helper buffs assist quite a bit for us soloers but the higher you get, the greater is the diminishing return for the buffs received making it tougher to level, ect ect.
Also for those would would be worried about the affect on PVP, I was always under the idea that full attention on 1 client was far greater than half attention on 2 clients. Back in the day I ran triple boxed clients and only pvp'ed on a single client because I was more effective.
Either way, I am incredibly grateful for all of the hardwork that the GM's have put into the server and whatever their decision is, then that is what it should be.