I also have long wanted a better GUI than AppleScript can provide.
Of course, this does require both you and your users to have Keyboard Maestro installed. IMO, KM is, hands down, the best Mac automation tool I have ever used, and it supports embedded AppleScript, JXA, Shell Scripts, and more. You can try it for free for 30 days (no limits). If you decide to buy, use this link for a 20% discount.
For more info about the KM HTML Prompt, see:
Good luck with whatever choice you make. If you come up with a good alternate GUI solution, please share it.