Can't. It's the only Pokemon in the game currently with Speed Boost, so it'd be a needlessly complex ban just to keep the stupid emu around. It's why Houndstone is banned when Last Respects was the problem. If Blaziken comes out with HOME, then MAYBE we can test Speed Boost, but it's most likely just going to be the stupid bird getting banned.
I'm 99% sure once Basculegion comes out, Houndstone is coming back and Last Respects is getting complex banned since it would wind up banning 3 Pokemon for its crimes.
So, then slap the band-aid on it now and disable speed boost Espathra. Nobody here knows what home will bring so you'd still solve the issue in the short term and have time to resolve it later.
If you're preparing for the unknown, I think the wider larger problem is Terastalization. It's particularly important to investigate whether that's something people want to ride out the generation with it now, so long as it's open to discussion.