Just under two hours and still haven't finalized my Jobs -_-
Thinking my Balthier has SHI/FOE.
At Lv99 as SHI he's gonna be at STR 81 SPD 38. Either KNI or FOE sub Job with Grand Helm, Mirage Vest, Germinas Boots (Jackboots replacement) is gonna be STR 81 + (6 or 7) + 12 = 99 or 100 STR, then SP 38 + 50 + 10 = 98 SPD, and finally (relevant if you're SHI/FOE), VIT 58 + 20 + 10 + 10 = 98 VIT.
So he's basically the FF Tactics Ninja... as SHI/FOE can hit hard either the Yagyu Darkblade or Scorpion Tail hhhh.
Basch has a better hammer combo rate but I saw some calculations on it, and it was like Basch got 46,000 DPS to Balthier's 45,000. With Genji Glove, too. Were you going Germinas Boots you'd probably do less DPS with either character (Germinas probably only better than Genji with Ninja Swords) but it'd probably be like 1-2% difference (versus the 3% difference or so with Genji Gloves).
Balthier would still hit harder though if you also just want to see big numbers hhhh. Assuming you're using the equipment above, it looks like they'd be at:
100 STR 098 VIT 098 SPD (Balthier)
103 STR 087 VIT 095 SPD (Basch)
096 STR 102 VIT 096 SPD (Fran)
103 STR 102 VIT 097 SPD (Vaan)
So I like Balthier's lack of wasted post-99 stats plus he's tied for #1 with ninja swords, basically tied (like less than 0.5%) with Ashe for #2 with hammers. But there's a real interesting idea around of combining SHI with something like RDM to make a more traditional self-healing tank out of it, but even then you lack the Shield Block 3 that KNI or FOE gives SHI. And out of all the FF (high combo) weapons, I think I want Masamune, Whale Whisker, and Scorpion Tail on separate characters so I can run all 3 + 3x Genji for fun if I want, and Scorpion Balthier, Masamune Basch, and Whale Fran works and has the lowest 0.5 combo rates for all. Only thing I sort of miss is that SHI/Mystic Armor would be fun for Yagyu + Dark Robes for Yiazmat.
Also, still not sure about my Basch as BSH but I'm still not sure the sub Job.
Basch at Lv99 is STR 76 / MAG 63. Then as Bushi he's 86/77. Lordly Robes makes that 91/92, and then either the Shishak makes it 102/97 or the Circlet 93/102. So to hit 99/99 Bushi Basch needs either 6 extra STR or 2 extra MAG, which would mean reaching either Battle Lore 14 or Magick Lore 16. So only Uhlan, Monk, and Black Mage let him hit 99/99 (max possible damage).
Flip side is those have less fewer synergies... just for a very marginal (if symbolic) gain. BSH/KNI... You'd end up 97/99 or 99/97, but you'd gain Shield Block 3 for when you start using Masamune I, you can combine Excalibur + White Robes for the huge amount of holy-weak monsters during the story, get access to decent spells to utilize that high MAG (though MNK does this even better and has more +HP Augments than KNI or UHL). Would be nice to grab something with buffs so he could help out with rotation of Haste, Bravery and Faith, Bubble, and then self-Berserk.
Being able to change Jobs out-of-battle a la FF Tactics would sure be nice but I sort of appreciate the weight that permanency giving the character decisions. How people played the OG versus how they are now is a pretty good case study for that 'respecs vs no respecs' topic we've had a few times here. Reminds me of back in Diablo 2, and constant 'evaluate my template' discussions. Adding a second Job to Zodiac Age was a pretty small but significant change.