I think it would depend somewhat on the failure mode of the original bank of SCRs.
If they failed short circuit, then no - because they'll just short out the "spare" bank too.
If they failed open circuit, then WHY? Whatever made them fail MAY have taken out the "spare" bank too.
It's a long time since I've worked with those devices, but I believe you can "turn them on" with a rapid DV/DT, which COULD see the second bank triggering simply BECAUSE the first bank triggered.
Finally, if you're going to put 14 on the board, why not just stack 'em permanently? Wouldn't that make it just about indestructable??