What's worth multiple bricks to me would be something that started with one way of directly increasing attack (assault or pride, arguably vigorous if you can make it work) and then pick up a second way. For example, stuff that end up with both assault and pride are highly valued. Bonus points if there's a third skill after that (like Shamash's weapon ends up being assault (M)/defender (M)/pride (S)).
Interestingly, Ascalon starts out already with Assault (L)/Pride (S); FLB raises the Pride up to M. So strictly speaking, the change from FLB in itself isn't as drastic. Still a highly desired weapon to have, but I'm not sure how many bricks it's worth investing in. The rest of the draconic eye exchange weapons are similar; FLB doesn't add a skill to them. It just strengthens the weaker skill. They strike me as the sort of thing where if you're in the business of wielding multiple draconic eye weapons, you're probably not averse to getting more eyes to just exchange for more copies as you need.

Looking over the hime weapon list...
Mars starts with Assault (L)/Defender (S) then picks up Vigorous (S)
As you noted earlier, both Odin and Raikou's weapons would count here; start with Assault (L), then pick up Pride (S)
Mammon's like Mars; start with Assault (L)/Defender (S), picks up Vigorous (S)
Shamash as pointed out earlier starts at Assault (M)/Defender (M), then picks up Pride (S)
Vishnu's like Mars and Mammon

As for the other hime weapons that pick up 3rd skills but are still stuck with 1 way of directly increasing damage? They're probably still worth a brick at least, but may not necessarily be worth 3 bricks?
Like Athena's starts at Defender (L)/Assault (S), then picks up another defender (S).
Or Marduk's starts at Assault (M)/Defender (M), then picks up Exceed (S)
Ale's starts at just Pride (L), but picks up Defender (S)/Ascension (S) together
Atum starts at Defender (L)/Assault (S), picks up Ascension (S)
Couple of weapons out there start with Assault/Defender then pick up Stinger, though Stinger's less popular.