Well, of course deploying this sort of tech would be a stupendously bad idea. It's a complete unknown; all we have are models that keep being proven inaccurate at best, and biased for political reasons at worst.
That's exactly the reason why *doing research* on it, on the other hand, is a very good idea. *If and when* it turns out that putting mirrors in space is actually what we need, I'd really like for the tech to have already been developed and tested.
There is one other MAJOR problem. Any mirror system in space that's big enough to affect the weather is automatically a terrifying WMD. And weaponisation of space is forbidden by international treaty. I'm sure that there are hidden weapons up there, but this wouldn't be something you can hide. If the USA tried to do something like this, even a comparatively small-scale experiment, Russia, China and everyone else would (with pretty good reasons) raise hell about it.