Party has already confirmed that it will be implemented at some point. So don't think of this idea as completely outlandish. And, we already know that Jagex can tell clients apart. And based on Arbiters theory on how their detection work, it's not that far of a stretch to assume that a player constantly switching between clients can be a flag.
I'm not saying that simply switching clients get you banned, I'm saying that get enough flags, and you get banned. So we should do our best to avoid flags.
Here's Arbiter talking about flags:
How to bot safely
So tell me, if you had the job of detecting botters, and you knew for a fact that botters used a different client to bot on.. Wouldn't you make this a flag as well? It's an easy one, many of the flags are easy ones.