You know, considering that this is a ZAIA produced item, wouldn't it make sense to have Valkyrie to use this, and essentially become Kamen Rider Valkyrie Fighting Jackal?

It's P-bandai anyway so they wouldn't worry about it not being sell well if they are so scared about 'female Rider not selling' angle.

I imagine that there's some story reason behind why she becomes Raider, as opposed to anything else. If the story needs her to be a Raider for a bit, rather than a Rider, than using a new Belt wouldn't make sense.
Having said that, that doesn't mean she won't gain a SlashRiser later, or just use it in her ShotRiser.

This makes all the sense, but since it's a expensive belt it may just boil down to that leaked key they said was for her

Let's hope Valkyrie will get a new form. I'm just worried that since she's a female Rider she'll naturally get screwed over.