AFAIK, Rough gas storage was closed not due to leaks that could be mended, but due to rust badly damaging the steel well casings. There was considered to be a risk of sudden failure that would be dangerous and also lose all the stored gas.
Repair is not viable due to depth below the seabed.
It should be possible to plug the existing wells with concrete and then to drill new wells into the same reservoir but the cost was considered excessive.
Increased land based natural gas storage is a possibility. Compressed gas underground in depleted gas fields. or LNG in above ground tanks. Both are expensive, attract NIMBYs, and are vulnerable to terrorists.
IMHO, the era of cheap and plentiful natural gas is over. Storage helps with any short term crisis but wont increase total supply, nor reduce average prices.
