Well the two storeis really go together. I mean the character in the second act is part of the main character dramatic need. (well comedic because this is a comedy) I don't want to take to much focus off the main character though. In the first act the main character is basically in every scene. In the second act the focus is going to spread between maybe three chracters.
I'm having the same feelings as everyone else. Like Dp said, without knowing some of the story it's difficult to give a solid opinion.
I have a few concerns about this.
First, you said that the character in the second act is part of the main character's dramatic need. My thought on this is that maybe you should introduce the second earlier on so that it doesn't feel like he or she just came out of nowhere.
Another concern is that if your second character isn't introduced until the second act, then maybe your first act is dragging a bit. (I can't know for sure of course), but normally by the first act your reader or audience know all the key players, they know where the story is heading, and what it is your main character needs or wants.
That last thing that bothers me is that you said in the second act the focus changes from the main character to the second character. IMO, I would not do this. First, it could become confusing and put a huge dent in your script. Traditionally the story is about your main character. In the first act we get to know this person, we become this person, we know what the goal is, we become sympathetic to this person's wants and needs. At the end of Act one, we have a pretty good idea of what it is the main character needs to do to gain his/her goal and the conflicts that stand in his way. To be yanked out and thrust into someone else's shoes just as the good stuff starts to happen, would be some what disappointing. You wouldn't only be changing the focus of the character but of the story. The story would no longer be about your main character, but becomes about your second character, his/her needs, wants, conflicts.
Just my thoughts. But like said, I don't know your story. My suggestion would be to read some scripts that resemble your own, not necessarily a comedy, but any script that introduces a second character in the second act. Might give you the answers your looking for.
Hope it helps.
Steph