First, thanks so much for the plugin. I use it, I love it, it’s great. It does exactly what it claims, and I’ve used it on thousands of images. If you had a paid version, it would be completely worth it.
My one ask would be integration to use the WP Offload Media hooks (or similar). I use that plugin to serve my photos from S3, and as it stands I’ve got a bit of manual effort:
Upload photos (generally via the WP app for Android)
WP Offload Media automagically uploads the photos to S3
Some time later, I sign into wp-admin.
Copy the photos back to the local server.
Remove the files from the S3 bucket so that the canonical source is local.
Use Image Watermark to apply the watermark.
Have WP Offload Media push the photos back to the bucket and remove the local copy.
If IW could use the OM hooks, I could avoid the wp-admin stuff and everything would just work from my phone.
I’d also be willing to subsidize such development, if it would help.