I agree that if we're about to do something that cannot work reliably, then a delay is simple and best (I've been using /autojoin -d3 in perform for most of my life).
Delaying perform would add more delay for people who use /autojoin -dN there, given that it's unreliable in the first place, I don't want mIRC to add more delay.
It was said multiple times over the years in the various thread about adding nickserv support, scripts are best for handling non standard or unreliable things and it's true.
I think the best mIRC can do for now is offer a 'scripted' solution via its UI: add two editboxes in the 'edit server' dialog.
-One defaulting to 'nickserv', used to indicate the nickname of nickserv (which can be any nickname in reality, e.g. Themis on Epiknet)
-A second one representing a wildcard (or regex, via a checkbox, for completeness sake) expression that mIRC would use to match against nickserv's notices
And a new switch for /server, like server -bg "nick expression", g meaning regex.
Edit: since the nickserv method only do /nickserv, the editbox for the nickname would be only relevant for the msg method