Shop App Suggestion: Sale mode, Online / Offline

It would be useful to have the ability to set the shop into different global modes.

1. For instance, setting the shop to 'Sale mode' would display all products with sale pricing (process product templates as though each product had the 'on_sale' attribute enabled). 1.1 A global percentage off all product prices (e.g. 'Easter Sale: 20% off everything', which is not uncommon on small e-commerce shops) could be applied to the original product price, negating the need for products to have specific sale prices entered, massive time-saver.
2. Other global statuses for the shop that would be useful are Online and Offline. The latter of which perhaps 301 redirects all requests for shop pages to either a maintenance page or site root. Useful for shop maintenance or in case of a hack/other emergency (whereby the site remains live but the shop disabled). I realise this is possible without Perch but I think it could be a useful built-in feature.