It would be denying new players the opportunity to play it as it was designed if it became solo. Such is the same argument that can be had for all level 50 content that can be soloed at level 60. SE kinda dropped the ball on this, and should have gated "level 50/60/70" behind completion of each MSQ, but that was defeated with the scenario skip cash shop item.
Likewise, I've played other MMORPG's that HAVE gone back and made multiplayer-mandatory story dungeons into solo dungeons, and the fun of those is greatly diminished, as they basically nerf it (eg lower the difficulty of the enemies,) while simultaneously making it harder for specific jobs (since now dieing results in failing the duty/reset of the boss room.)
Now what might be a less-irritating way to solve this is to combine the two. They have a 2 hour time limit, break those into 20 or 30 minute parts, and then have "AI party" in the menu next to "undersized party", selecting the AI party brings you to a second menu:
Slot T/T/H/H/D/D/D/D/D (yes 9, for duties that have two tanks or one tank 5 dps)
If you have a command squadron, you can place them in any of those slots they fit the role for.
If you do not have a command squadron (or none are leveled to this point,) it instead allows you to put specific NPC's (eg Alphinaud,Alisaie,Y'shtola, Thancred, Yda, Papalymo, etc) that are available at that point in the storyline (to avoid confusing cutscenes.)
So whenever you pick a non-roulette duty that you haven't completed, you can either "wait for more party members" or "play using AI party" (no tomes rewarded) just to see the cutscenes without players being obnoxiously wanting you to skip it.
