Ah, now that's an idea.
Or, how about a hack to make Sims drop dead as soon as they reach permaplat?  It would certainly introduce a new element of gameplay, wouldn't it?  The only problem is, I have no idea where or how to test the aspiration benefit points level so you could do that.  Maybe it's hidden in the LUA files.
--- update --
AHA!  Found it. 
[global 0x0612] Long Term Aspiration - Modify Points 
--- UPDATE AGAIN ---
Okay!  I have a hack ready for test.  It seems to work for me.
http://www.moreawesomethanyou.com/smf/index.php/topic,12387.0.htmI divide the number of new points by three before adding them to the lifetime aspiration total.  It seems to work, although I still have some questions.
With the hack installed, I created two new Sims in CAS, Jelly Neptune and Merv Neptune, and placed them on an empty lot with Insim.  I self-impregnated Jelly and then rushed her through to the birth, and saved the game, exited.  She did not have the "Have a Baby want."   
In Simpe, I saw the following values for their lifetime aspiration points.  Simpe, for some incomprehensible reason, displays them in hex, so I have translated to decimal.
Merv 9880
Jelly 10280   ---- that's 400 points more than Merv.
Eddie (the baby) 1800
For reference sake, all untouched adult townies come with 9870 aspiration points to start with.
Next, I removed the hack and restarted the game.  This time, I self-impregnated Merv and rushed him through to childbirth.  He did not have the Want a Baby want either.  Then I saved the game and exited.
Now Simpe showed points had changed as follows:
Merv 11090  -- that's 1210 points more than he had before.
Jelly 10290  --- that's 10 points more.
Eddie  1800
Marietta (the newest baby)  1800
From this, it appears that the unchanged Freetime gives 1200 points to a Family Sim for having a baby, beyond whatever extra points they may get for actually having the Want a Baby want.  But with the hack installed, Jelly only got 400 points.  
The extra ten points are bothersome.  What are they for?  I don't know.  If they are automatic for "New member added to the family" then you would think Merv and Jelly would have only got three points extra the first time.