Using Square for backup processing?

Has anyone ever looked into using Square as a backup for credit card processing? We currently do not have any external credit card processors- everything is ran through Tessitura. So when Tess is out, we don't have a way to process credit cards easily. We are a Vantiv client, and part of my contingency project is looking into acquiring external EMV readers from them, but I'm absolutely dreading the process because of terrible customer service experiences I've had with Vantiv in the past.

I thought of Square and it looks way more appealing to me. From what I understand, we can get 15 of their magstripe card readers for potentially the price of one EMV reader from ingenico or verifone (I'm assuming this is what Vantiv would set up up with, and I've heard that those readers can cost as much as $500+ for one device. This may be incorrect though, I've just been really dragging my feet to try to get a quote from them.) I know Square takes a cut of sales, but I'm almost thinking it would be worth it in the end to be able to do sales EASILY in a moment where we would potentially be doing zero sales.

I'm not concerned about it having any connection into Tessitura- in the event we would actually have to use the Square devices, we would go back into Tessitura once up again and record the sales. It's literally just to get payments- particularly at our GA performances that would absolutely stink to have to turn people away from. 

I welcome any feedback! I know there's been posts about Square before, but I don't think any of them discussed it being used in this way.