I don't think this is necessarily the best way to go about it.
It's a million times easier to find more SR weapons in different types than it is to get more himes for your squad. If your squad is all DPS and no debuff, or 3 healers but no damage, you'd want to correct that through the Heroic Soul to balance out your team. The SSR weapons you have will still count as good stats even if they don't match your hero, but you won't get a whole hell of a lot out of adding Andromeda to a team with 2 healers already on it just because she can use a Lance. She barely even attacks, it's not like the damage is a huge boost on her. Compared to Arthur or Siegfried, where they ARE the damage, it wouldn't make a hell of a lot of difference.
Unless you're planning to buy a bunch of gacha pulls to even out the himes on your team you kind of have to build around what you've been given.