There is a plugin/tool that allows for image editing (more advanced than adjusting hue/saturation and so on).
You can also make image adjustments right in the editor:
If you’re wanting to batch/bulk edit those values, you can utilize “Bulk Edit via Property Matrix” after selecting your desired assets, then right-clicking (found under the “Asset Actions” sub-menu).
If you’re wanting to go further than that… Well, Unreal Engine isn’t an image editor. It totally can be, but I’d rather Epic and our lovely community of contributors concentrate on the engine, rather than spending cycles dipping into an already robust field. Personally, I find the ability to use Photoshop PSD files, and have those assets automatically updated in-engine after I make edits in Photoshop pretty slick. The same goes for Substance stuff.
Ultimately, if you’re after automation/batch editing of image files using the engine, it’s possible already, via Blueprints and whatever tools you have in your pipeline. Any design choices Epic made concerning making a “quality of life” feature to expedite that, would not be wise. Too many of us have our own toolchain and pipelines, and Epic spending time to cater to a single path would likely not meet the needs of those not using Paint.net, Photoshop, Gimp, 1995 Windows Paint, so on and so forth.
At the end of the day, we have dozens… Well, hundreds of tools and utilities that cover all our bases when it comes to image editing and batch operations. To answer your question (what do we think about your idea), it’s not needed. We’re good. I don’t want Epic and friends to make a 3D modeler, an image editing tool, DAWs, etc. I want them to keep making the engine awesome and stable.
Also, this forum section is for the community to share their tutorials, resources, etc.