Not sure how anyone missed our three way 30 post talk a page ago?, but knuckle and sword will be the BEST if you have the ideal setup.
Not everyone reads every page when you wake up to several new ones.
Second, the only way that would be better is if you have Delita(Base) and they allow Leon's TM to stack(I'd say a 50/50 chance at it right now). If not, you're stuck using the Enhancer. 82 ATK vs 98ATK. You'll always be 16 ATK less regardless.
Going over a few of the set ups.
No Stacking(No Base 5 TM)
Sakafu vs Enhancer(+16ATK)
BM vs Leon's TM(Flop)
Rest is the same
BM is better.
Stacking
Sakafu vs Enhance(+16ATK)
BM vs Leon's TM1(Flop)
30ATK vs L TM2(+20% ATK, minus 31(Potted ATK is 156)
LTM is better(Required 2)
Stacking + Ramza TM
S vs E(+16)
Brave Suit vs Demon(+14)
BM vs LTM(Flop)
30% vs LTM2(31ATK)
At this point, it's a 1 point difference. You need the 3rd to make it clearly better(Required 3 for better, 2 for equal) if you have Brave Suit.
Leon's TM seems better suited I feel for Giglamesh or Luneth who naturally get that sword bonus. Making up any difference between the two. And just noticed your edit, but Firion can't use Heavy Armor.
So some quick napkin math.
Stacking and without any base TMs
S vs E(+16)
BM vs Heavy EQ(+78)
30% vs TM1(-31)
30% vs TM2(-31)
So it's not even close anymore, BM will win by 32ATK pts.
With Delita's Sword
S vs M(-20)
BM vs Heavy EQ(+78)
30% vs TM1(-31)
30% vs TM2(-31)
So it will edge it out by just 4 points. This is also me not factoring in Ramza's TM, where with it and Katana, you will end up 9ATK ahead with Katana + Brave Suit.
Firon's best will still be Fist + Katana, Two Belts, DW, BM, and 2x 30%. And if you have Ramza and Delita, better with Katana and Ramza's suit. Which is his ideal high.