I don’t think we would require being “paid back” any income lost during a (defined) period of hardship for the company, personally I would already be satisfied with not permanently give up any terms and conditions (which we would indeed never get back). In other words, any concessions made (such as a salary sacrifice) should be limited in time, after which an automatic return to current terms and conditions occurs.
Anything else is just trying to take advantage of the current crisis to permanently cut unit costs and our income/quality of life. If they don’t need our labour, redundancies are natural; but if they want to keep the frontline workforce intact in view of making a killing post-crisis, then asking for permanent concessions is not acceptable.