Of course it would have to go in the constructor but you get the point. This would make it work on windows without initialization parameters. If including system is too much overhead the function from system could be modified to be 4-5 lines and added to cache lite.
Your idea is quite good. But I really don't want to include another package (optionnal is ok) in Cache_Lite for speed reason (for example, if you include at each time PEAR.php, perfs are twice less good). So if you can provide such 4-5 lines, I would be very happy to commit them :-)