Like lots of other businesses that have reduced or closed down, there will be a concern that there might not be enough business to restart later. I don't see why the Railway should be cushioned from this possibility when many other businesses do not have this luxury.
The 'general principle' should be that the subsitutions are the most effective in saving train crew, taking into account shortages, passenger usage and ease of substitution. Not worrying about whether suspension may be permanent or otherwise.
That's all very well but the railway isn't quite like a lot of other business is it? If a baker's shop closes down, there'll probably be another one nearby instead. Ever if there isn't, it is reasonably easy in a lot of cases for another one to open up in future when demand is more predictable. Even the Government recognize this which is why huge subsidies are currently being paid to keep a service running, much to the ire of the Treasury.
Close the railway down or close a station and it can be enormously difficult to get it going again. Look at those stations in Staffordshire which were "temporarily" closed in Railtrack days for West Coast Main Line upgrades. Twenty years on can I get a train to Norton Bridge or Wedgwood? No, I can't. Stone eventually re-opened but only after a fight by the locals. Promises broken, trust lost.