Hi!
Well, making the left/right/hidden concept different would be really some amount of work to do.
...30 minutes later...
Okay, maybe it isn't. I've prepared a patch, which I can sadly not try without my development machine.
Anyone willing to testdrive it? What it should do is support a new config.inc.php template option called 'sidebars'. This holds a comma-delimited string value of sidebar names. Like "left,right,top,bot,hide". Note two things: Don't use spaces, don't use descriptors longer than 6 characters. Make sure you also use the default value of the $template_config['sidebars'] to indiciate an order.
Have a look at the docs/NEWS entry I added to describe the option. I hope it works as smoothly as I imagine it to work.
You can then use your custom side name ("top" or "bot") as usual in the smarty function call: {serendipity_printSidebar side="bot"} etc.
Here's the patch:
http://garv.in/serendipity/pluginmanager.diff
A TGZ including those files (from an 1.1-alpha4 version):
http://garv.in/serendipity/pluginmanager.tgz
Carl, I hope you like it. You really know how to motivate me, do you?

I think this is a MAJOR cool new feature to the theme configurator in the 1.1 branch.
Best regards,
Garvin