Event Bridle Flash

The horse I'm buying is currently ridden in a flash bridle. I saw that many horses at events (we would be eventing frequently) were in figure-8 bridles.

Could I switch this horse from a flash to a figure-8? Don't they serve the main purpose of getting the horse to stop avoiding the bit? Of course there are other reasons - but if I switched from a flash to a figure-8, would that be ok or would I run into different problems?

(This horse was always ridden in a flash so as the lady trained him, he wouldn't learn to avoid the bit.) I still want to keep him on that same path, continuing to teach him without him figuring out to avoid the bit, so I want something like a figure-8 or a flash.

Please don't tell me "go ask your trainer and see what's best" I obviously will, no worries - I just want a quick opinion.

Thanks! xxx