Right. Using a return value from an alias like that is even better. I was just showing what was basically a 1 to 1 representation of what was requested.
To the OP: It might take a little while to make changes to scripts already written, but not that long and you'd have to make changes regardless if some other method were created. All you're change are the SUB's, which aren't hard to find or edit. Any other changes would have to be made to both the SUB section AND the rest of the script and would be done for both your way and the /set way. And, for that matter, your SUB sections would have to be written anyhow. I don't see that it would add much of any extra work.
Considering mIRC isn't likely to add anything new this version, you're going to have to wait at least 6 months or so before there would be any chance of it being added. Instead, you could just use one of the two methods given and then you can have your modular ability immediately, which means you will have fewer scripts to edit (you'll have more if you wait until something like this gets added... if it ever does). In the end, you save a lot of time using one of these methods. And once you have your current scripts updated, anything new can be done this way from the start if you plan ahead a bit.
Also, considering the way I showed you does pretty much the exact same thing other than using /set instead of /var, I really doubt this would be added just so users can use /var instead of /set. Throw in drum's example and it's even less likely. I could be wrong, but if it were me, I wouldn't wait and hope for it to happen and would just use what was already available.