IPS Patch Merger
This actually has nothing to do with Fire Emblem, but here we are.
Like the save compressor/decompressor, this tool runs entirely locally in your browser and you can even (but don't have to!) save a copy of the web page for offline use.
You'll want to select multiple files; a single file will probably just get you the same thing back.
This tool does no error checking at the moment, so if you try to merge things that aren't actually IPS files you'll almost surely get total nonsense.
In addition to the above buttons, you can also probably drag-and-drop a folder to get a best-effort attempt at decompressing all the files inside, given that you have a reasonably modern browser (but also I didn't test this on anything other than Firefox).
Error reports appear below this line.