Matt. Assuming they have good brainwashing skills, a tool like the Sun goddess would make the Changeling empire much more powerful.
 
It’s easier to just kill remove obstacles, but if you have the ability to completely render them subservient to your will and they’d give you a good power buff, why NOT?

Excuse, but does Celestia even look like a drone? Are you going to assume that Changeling-o-magic can even begin to nerf a pony’s powers, let alone that of a Sun Goddess?
 
And how would it even seem like a good idea to a villain to even attempt to convert Celestia into a Changeling? Or even any of the Mane 6? To me, it would be easier to just outright kill, rather than risk allowing a partial transformation to occur - something like this:
 

 
Context, specifically the second paragraph under Plot
 
Sorry, but my suspension of disbelief draws the line at converting food sources into creatures that consume said food sources. Doing that would make the Changeling’s food shortage problem WORSE, and it completely undermines Chrysalis’ motive for invading Canterlot.
 
Chrysalis may be a really stupid villain, but she isn’t that stupid

sixtyfour215:
 
Maybe it’s just for the evil gloating potential of turning your enemy into one of your drones.

God, for a .gif, it just scared the hell into me. Hope noone will make a trailer out of this.

@sixtyfour215
 
maybe she wanted a wife. . . or concubine

Damn…got chills.

…I want this to continue…

@Background Pony
 
O_o

I wish this would happen to Luna

animated
 
sweet

Why would crysalis want to changelingify her? Wouldn’t she just overpower her and become the new changeling queen?