I like the IDEA of a Lancer tank.... but it would thoroughly require the entire armory system to be modified....
There are 3 tiers of tank gear...
1.) the GLD/MRD gear that is interchangeable.... Darklight included
2.) JOB specific gear... AF1 & 2
3.) The gear that LNC/GLD/MRD can equip that is light/heavy armor... cuirasses, hauber's

If the LNC was to open up a 2nd JOB as a TNK... the whole system wouldnt mesh...

The 3rd tier gear would become obsolete.... even for Low-mid levels... why get that gear if the heavy armor would now be equipable, or worse off.... the TNK LNC job wont have access to the Heavy Armor options, and the game will have to create a whole line of gear types solely for the LNC TNK... and not just high level, for the 30/35/40/45 tiers as well, on top of ilivl 55/60/70/80/90 and future gear levels.... that would be alot of modifications to force a TNK role as a secondary role of a DPS class, let alone matching new emnity generating abilities

I could see a role like Knight coming off of the LNC class.... like Swiss Army Knights that guard the Vatican. Or a Pole-armed Jouster.... and could be used as a tank class off of the LNC, but again, what will happen to those light/heavy armors that only the LNC/DRG will wear in the mid levels that are one of the reasons I leveled a DRG to 50... cool gear sets that will no longer be a viable option unless you go straight DPS DRG, which lets face it, there are enough high level DRG's already