Yeah it's really hard to design any polearm more complex than a spear to be safe for sparring with. And even those spears are nowhere near as safe as swords like rapiers or sabres. Or even longswords.

I've sparred with large poles with bits of pool noodles stuck to the end to simulate spear tips. It's very fun and fairly safe (as long as you're extra careful with any butt strikes). But it doesn't feel anywhere near as realistic as the rapier sparring we do.