The default template for PO will always be the standard choice, and currently, there are limitations to customizing purchase orders (PO), specifically removing the signature line in QuickBooks Online. Instead of disregarding your excellent idea, we encourage you to send your feedback to our Product Development Team, as we highly value your suggestions. Here's how you can do it:

1. Go to the Gear icon.
2. Select Feedback.
3. Enter a brief description of your product suggestion and click Next.
4. Type your email address.
5. Once done, click Send Message.

Also, feel free to visit our Feedback forum page to see a list of other QuickBooks users who have already suggested this feature and for the recent updates in QuickBooks.

Here's an additional guide about customizing your forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Drop a comment below if you have other concerns or inquiries about QuickBooks. I'm just around to help. Take care always.