The problem is with recurring payments. If you used this approach and 1/3 of your customers were initially billed through Stripe, then if Stripe bans you then you can't charge the next month's bill through something else because you don't have the stored data for it, you have to ask them to re-enter data in another processor's system.
Another wrinkle, in practice, is that you can often negotiate significant discounts on fees, based on volume, if you've got enough of it. Yes, including with Stripe and other places that have fairly-transparent public pricing—the big-boys don't pay those rates, they pay lower ones negotiated with a sales rep.
Splitting up your payments reduces your volume with each one, which can mean you're paying higher rates overall. Or, if you go the "keep an unused alternative on standby" route, you'll likely at least have some initial traffic that pays higher public-pricing rates until you can convince them to give you a better rate, and put it in effect.
Still might be worth it as a kind of insurance premium, but it's something to consider.
