Tank and healers are a little more unique in design than DPS in FF14. I mean apart from MoP and WoD tanks in WoW, traditional MMO tanks don't care about damage. Healers in FF also function very uniquely, though not completely unheard of Age of Reckoning also had healers with very offensive capabilities. Damage on the other hand don't really have any innovations, Damage is the most traditional MMO role in FF14 the only thing that really sets them apart are ways they go about their priority. Before level 30 all the damn Melee and the tanks feel pretty much the same with MNK feeling like the only true exception. I mean later combo stings change in slight ways, and the amount of DOTs and maintenance buffs/debuffs differ from class to class. However the unique class feels seem to really come from the 30+ skills.
With that said, if SAM was a traditional Melee DPS:
They could easily go the duel wield Samurai route, perhaps have the ability to do two combo lines at the same time that merge together as a finisher 1,2+3,4 lights up ability 5 1,6+3,7 lights up ability 8. So main hand combo line, off hand combo line, finisher together with both swords.
The Stances as I stated before and then adding something else to give them their own unique twist.
Both of these -could- be achieved as Tanks. I personally would like to see a true counter part to the added RDM, the caster that dashes into Melee being introduced with a Melee that dashes out into ranged. As I stated in another thread on this subject a Gunblade SAM could easily accomplish this, this could also match the design intent of AST and DRK, who each represent a midway counterpart of WAR/PLD and WHM/SCH prospectively.
Looking at this a little deeper our current Job spread is as follows:
Tanks:3
WAR
PLD
DRK
Melee:3
NIN
DRG
MNK
Ranged:2
BRD
MCH
Caster:2(3*)
SHM
BLM
RDM(*)
Healers:3
WHM
SCH
AST
It almost feels assuming we're going to keep the Tank, Ranged, Caster, Melee mold that the next classes added in Storm blood would be a Ranged fighter, however all information leads we have suggest SAM at this point, and we all know they're going to do the 17th century SAM class fantasy and not the 10th century could very easily be a ranged class.
However, if we view the classes in more of a ranged vs Melee vacuum.
Tanks:3
WAR
PLD
DRK
Melee:3
NIN
DRG
MNK
Hybrid: (1*)
RDM(*)
Ranged:4
BRD
MCH
SHM
BLM
Healers:3
WHM
SCH
AST
Now if we broke up the classes this way, SAM could make the Melee to ranged ratio 1:1 This is of course ignoring the fanfest information that RDM will be considered a caster. Which I also feel like RDM will be more caster than Melee...
Meh, at the end of the day we could speculate talk about balance of class roles, and identity and none of it amounts to shit because all of those above stated things can be changed by the creator.
I mean if I had my way I'd change the current Meta and Class feel/function as little as possible.