I totally agree with the response from ActiveState: there is nothing stopping you making a patch that implements this and sending it to p5p - this is likely to be far more productive than moaning about it here. I also think that asserting that you make money from selling applications written in Perl and then essentially demanding that someone do something for free to help you make more money is at best tasteless.
As to your original suggestion I personally find it entirely without merit, firstly it assumes that all Perl programs are run under the CGI and need only to run for a short time, this is patently untrue. Secondly what you are describing is not a bug in Perl, but a failure on the part of the server administrators combined with the differences between Windows and Unix. IIS has configuration for Processor Throttling (a limit on the amount of time a process can take on the processor) and Script Timeout - it is the responsibility of the administrator to ensure that these are set appropriately for the kind of use that the server will be put to.
It might also be noted that the alarm() function is not implemented on Windows, so this would also need to be remedied before implementing your suggestion (Okay, I discover that it is implemented with 5.8.4.) I would suggest that, if the IIS configuration is not sufficient to your needs, you (or the server administrator) should create a small wrapper program that can control the execution of the CGI program.