It seems you answered your own question.
Decals go on top of power or wet. Clear goes on top of decals and base. Doesn't matter if the base is powder or clear.
If you want to get fancy, clear only over the decal and not the base.
You can't do a powder clear coat over decals, agreed? To be precise, not without wrecking the decals.
I can put decals on powder coat, then wet paint over the decals (proper type of decals selected, of course). Everywhere I've read is that a wet coat over powder isn't very durable. One would think that you could scuff up the powder coat, put on the water slide decals, then rattle can clear coat over them. But I haven't run into any posts or pictures showing this done. It seems reasonable.
"Pics or it didn't happen". I'd like to ask the person that's done this how it turned out.