argv0 still makes a great point that if you were to use something like this, which is highly cosmetic rather than actually beneficial, that you would be limiting your script to only newer versions of mIRC. Maybe a scripter wouldn't care about that, but I think most people want to maintain compatibility with older versions as much as possible until it becomes inconvenient such as not being able to use $v1 (something that is very beneficial).
As to your first comment about two commands... based on your thought that one command should do everything, then why bother having two commands at all? If you're going to use that reasoning, then let's just drop one altogether and put everything into one command. Sure, it breaks scripts, but it is better than saying that one command should do everything and the other should do very little. Either two commands should do two different things, or there should be one command.
That's not really a good point at all and your example of using $v1 is especially bad as it's identical to the much older $Ifmatch. $v2 would've been better :p
As you stated yourself it's up to the scripter to decide if compatibility is important.
I would quite agree that there's no point in having both set and var if this was an alpha version of mirc v1.0, but as both commands have been around for so long it's not an option to remove them. As both commands do very similar things, not allowing var to set timed unset variables is a very arbitrary limitation. I would say it makes more sense to allow /var to do everything as changing the format of the /set command to allow multiple variables could affect backwards compatibility.
The argument that /set can already do these things became somewhat invalid when /var -g was added.
Again, not sure why a simple and reasonable request is receiving such opposition.
Typed this post on my smartphone so sorry if formatting/spelling is dodgy!
