Genderswap Primarch name shortlist...

Lion el'Jonson:

The Lioness.

... I don't know who would be a similarly on-the-nose female poet.

Fulgrim:

Perturabo

Perturaba?

Jaghatai Khan:

Alakhai Khatun (for Alakhai Bekhi)

Mandukhai Khatun

Leman Russ:

Leman Russ. It's exactly as stupid a name for a woman as it is for a man, so why change it?

Rogal Dorn:

Konrad Curze:

Sanguinius:

Sanguinia. Duh.

Ala ("wing") for an alternate.

Ferrus Manus:

Ferra Mana. (Again, line of sight dumb name.)

Angron:

Furia (not super fond of this)

Erinye

Alecto/Alekto (favorite option; "endless rage")

Dira

Tilphousia ("vengeful destruction")

Angra (duh!)

Roboute Guilliman:

Mortarion:

Morticia?

Ereshkigal

Magnus the Red

Miranda (worthy of awe) the Red

Horus Lupercal:

Ishtar

Athena Lupa

Lorgar Aurelian

Not sure for a first name, but Aurelia definitely works for a second

Vulkan:

Pele

Corvus Corax:

Corvus Enca (the only plausibly female name from Corvus species)

Enca Corvus

Enca Corax

Alpha Legion

Alpha and Omega, why not?