Can airport handling agents pay out EC261 to a bank account immediately?

All airlines will have their own policy on exactly how the refund/compensation process is handled. If you want a real firm answer, see the policies of your chosen airline for details and contact them to clear up any questions you still have after doing so.

But having said that, what you're asking about is extremely unlikely to differ between airlines. This is just not going to happen.

Airlines don't make a habit of paying out fees where it's avoidable. Even small airlines have entire accounting departments whose jobs include - amongst other things - verifying that all refund/compensation claims are valid before they're paid out. You may know perfectly well that they have no choice but to pay out in your particular circumstances, but you could claim they have no choice regardless of whether you're right or not. Doing so won't stop the airline from making sure of it themselves before approving your claim. It's unlikely that anybody you speak to at the airport is authorised to approve EC261 payouts (and even if they may be authorised to offer general 'goodwill' compensation for other matters), and it's not a given that they'll be particularly inclined to do so there and then even if they are authorised, especially if they suspect you've intentionally manufactured the situation.

Even if you do find somebody who can authorise the compensation, I still wouldn't expect to receive it instantly. I made a claim after a cancelled Easyjet flight in 2018, the message notifying me its success stated that I would receive the sum "within 14 days". I don't remember how long it actually took, but it was certainly several days and possibly close to the end of the 14 day timeframe. I see no reason that handling it at the airport would speed up that process - they're certainly not going to just give you cash.