Let's see, when only considering "good" women:
Usefull females (can fight) by Iga :
Yoko Belnades
Charlotte Aulin
Stella (but still victim of vampirism)
Loretta (but still victim of vampirism)
Shanoa
"Usefull" reimaginations of earlier characters by Iga:
Maria
Sypha
"Usefull" females not reimagined by Iga:
Carrie Fernandez
Sonia Belmont
Carrie's cousin (but still a victim of vampirism)
"Useless females" (can't fight) by Iga:
Liddy Erlanger
Mina Hakuba
Sarah Trantoul
Lisa
Elizabetha
Rosalee
Julia
Misc female Wygol villagers with just as many "useless" males, so they kind of cancel each other out.
"Useless females" before Iga but re-imagined by him:
Annette
Tera
Iris
Rondo sacrifice girl
"Useless females" before Iga but not re-imagined by him:
Legacy of Darkness sacrifice girl
Simon's bride in Haunted Castle
Ada
Rosa (probably couldn't fight until turned to a vampire)
"Useless males" by Iga:
Hammer (ironically)
Vincent
All male wygol villagers
The Merchant / Master Librarian (might not count, as they're somewhat of enigmas)
And some others created by others, but "overseen" by Iga
Michelle Danasty (novel) - Usefull
Illyana Riktor Belmont (Belmont Legacy) - Usefull (but still got captured)
Pasha Totoyan (Belmont Legacy) - Usefull
Liza (LoI manga) - probably usefull
Justine Gandolfi (LoI manga) - useless (vampire victim)
Angela (Pachislot) - usefull
Zoe Belmont (Order of Shadows) - usefull, but not shown fighting
Dolores Belmont (Order of Shadows) - usefull, but not shown fighting
Lady Gunner (Arcade) - usefull
Little Witch (Arcade) - usefull
didn't get any "worse" during Iga's reign, though it does depend how you count them.