Well the "hotlink jump to line" could already be done. Not saying it shouldn't be added, but you can do it with some scritping/dlls. You could setup a hotlink for something like:
*:*(line *, *)
That, to my knowledge would catch all mIRC errors that have a line number specified, and it really shouldn't catch too many false positives, unless people paste script errors in a channel, but you could work around that with a little more complex checking (perhaps some regex?). The hard part would be the jump to line #. But basically you'd need to use a dll that would get the handle of the editor window, then tell it to set it to jump to the specific line. The dll portion of it shouldn't be more than 10 lines of C code, and the mIRC script portion shouldn't be more than 5 lines of scripting. Like I said, not saying it shouldn't be internally added, just saying if you really want it, you can do it already.