imho, smile
if you’re setting up a new system, routed from two identical laptops,
then, that’s a new system, and requires new ideas/technology/gear like any new live show system…
like you say, a clone laptop to switch to, is just another laptop, and much less to duplicate
(you may even have it already)
i’ve heard stories…even kraftwerk has crashed on the first tune,
and then everyone heard the startup 'bing
a live redundant failover may involve having two identical systems,
both the same (2 of each, all the gear and laptop)
or, you could just keep the tracks on your phone, and dial them up in case…
(the mics may still be working)