I recall when a STOLPORT at Sheffield was announced jumping on the Plymouth STOLPORT and subsequently London City STOLPORT theme, if I recall correctly Sheffield City Airport was the brainchild of a BCal, or ex BCal, pilot.
LCY started off, literally, as a DHC7 runway and, over the years, it has been extended and extended, had the runway remained at it's original length then I have no doubt that it would have, before now, met the same fate as Sheffield and Plymouth.
On the subject of PLH they extended the runway to, literally, maximum to accommodate DHC8 and ATR42 size and performance aircraft but alas these sizes of aircraft operations couldn't compete with the LoCo operators of larger, more economical per passenger, aircraft and last year PLH met it's fate.
So if Sheffield re-opens is a runway extension possible whereas, let's say, Q400 etc. operator(s) could operate or is it likely to remain restricted to 'Puddle Jumper' operations making it nonviable before it may even reopen?