I think melee will be possible with the way we are doing our new server architecture.
Normally, in an MMO type server, melee is very restrictive due to lag, and MMO style,slow server ticks (MMO servers only update on a slow tick rate. WoW was up to 5 seconds per tick for some types of events.)
Overwatch, a shooter and non-MMO style server, had a tick of 21, which was increased to 60+ after users complained and they found a way for high bandwidth PCs and low bandwidth PCs handle different rates of data updates.
Firefall was an unusual case. Not only did it have a slow tick rate like MMOs, it also used CS (Counterstrike) style lag compensation. This meant that everything you saw (monsters, other players), was slightly in the past by up to (I forget the exact number) 350ms. This made melee impossible to feel good. It also made it hard for things like monster to pause or stagger if you shot them. This made NPC combat feel terrible.
Em-8ER will feature a brand new server architecture. We won't discuss the secret sauce because we don't know if our experiments will work yet. We're going to be doing a lot of trial and error. But the goal is to allow for very, very responsive shooting, NPC reactions and yes, melee attacks.
The Thumper is meant to go hand to hand with Kaiju. Tsi-hu, in beast mode, are meant to melee your Omniframe. We're going to be trying our best to make it feel great.