I think the problem here is you just want mIRC to do everything for you, and if thats the case then scripting isn't needed.
It is a suggestion, not a problem. If he wants mIRC to do that job for him (to support ctime on /timer, which I'd want too), it doesn't mean he wants it to do everything for him. However, if this is a personal opinion of yours, I don't see why do you bring it since it's obviously not going to improve the discussion.
/timer -c [#channel]
trigger the timer only if I'm on #channel
Unrelated. I don't see anything here related to combinations of more features (IRC/ON JOIN, in that case) into /timer's parameters. What I see is a suggestion to add another time value to /timer, following its pattern and making sense, since mIRC already offers one (HH:nn) - which could be easily scripted as well. Then..
All of those suggestions are just as equally valid.
..this is an opinion of yours. From the point of view of who wants mIRC to do everything for him/her, they might be equally valid. But since you brought an idea not really related to the suggestion, they don't seem equally valid following it.
That script is no more complex than a simple "hello world"
Yeah, it isn't. It doesn't work, anyway. zac shows one that works and it's even simpler, but it doesn't offer all /timer's features, that's something I suppose Doomstars has pointed out talking about simplicity. In this case, simplicity not only to script it, but to "port" it and make use of it too. If he's not, I am.
Anyway, a lot of small features that could be scripted are now built-in, yet, from what I see, nothing has worsen about it to who disagrees or has never needed its inclusion. People who agrees with it and/or needs it end up using it, justifying such small additions. This is only another one, which I think that would be used. As a suggestion to Khaled, others should at least not diminish it.