You all probably know that "Dragons will also automatically kill dragons already ravaging kingdoms they strike."

Has anyone ever worked with an allied KD to send a weaker dragon to replace a stronger dragon?

To clarify, let's say my enemy sent me an emerald in war. If I had a friendly KD start a sapphire dragon aimed at me several days before the war, they could send that sapphire to replace the emerald. The life would be significantly less because of the type change and the because it was sent into another KD's war.

So, have you seen it done? Is it a feasible strategy?