I just find it a lot of aggravating micromanaging, unless Bioware is good this time about actually telling us where the AOE for this sort ability would be, and where it always is. But I prefer a "sole" melee and otherwise ranged, unless the melee warriors are single-target exclusive, or they have ranged AOE (like fireballs).
You do make a persuasive argument about the potential of turning the KE into a close combat specialist. It just leaves me the problem of what to actually do with a warrior.
Friendly fire is indeed a problem when dealing with a warrior and a melee-mage, but I think it will be manageable. I like to switch things up in battle, so I have no problem with odd party compositions and builds. For example, I am planning to use Iron Bull as a S&S warrior who focuses mainly on party buffs like Horn of Valor. If I put him on the same team as an Ice Elemental KE, the two of us can theoretically switch off between buffing and ranged attacks while the other 2 party members do whatever (probably ranged damage and combos)... Bull will have Harpoon ready just in case an enemy tries to target somebody I don't want them to, or the Inquisitor can freeze them in one of many ways. So long as the enemy is locked down at all times and every party member can contribute to or exploit this in some way, I don't really care what class they are...
So it really depends on how each party member is built... there is probably an optimal way to do this, but I probably won't be following that path. Deviating from standard builds and tactics keeps things interesting for me... the main idea is to make use of the KE's versatility as a hybrid class and to make sure that the party supports whatever the KE brings to the table. YMMV of course... I understand that this type of play style isn't for everyone.
One other thing... Shield Wall has an upgrade that boosts the Armor of nearby allies when used, so it seems that at least some of the skills were designed with multiple melee party members in mind...