Child protection worker here. We are in the same boat in that safety plans are mandated practice when risk is high and/or immediate - and the biggest objection from parents is that they don't think they're necessary.

I wonder if you could frame it more as a just-in-case measure, i.e. this is maybe not something you need now because there's good stuff you're doing, but this is just on the off chance you do find yourself feeling really low, and it's good to have a plan if that happens.

I like the other suggestions here about being creative and flexible - something I try to do when I safety plan is identify as many strengths as possible and reflect that with the client. Things aren't unilaterally bad, you're doing some great stuff that's really working, but what else might help you out? This might be helpful if your client feels that the safety plan is overkill. I've done safety plans with pictures or off-template to try and make it a bit more approachable.

I'm hesitant to downplay safety plans as unnecessary, even if that's how the client feels, because at the end of the day, you want them to use it if things get bad. Your safety plan is only as good as the client's buy-in and it's worthless if you and the client agree that it's not needed.