Please don't force HTTPS in the software. I'll explain why I'm making that request here.
First, it's easy to force HTTPS in the apache config for the vhosts, I've done this. It's a simple matter of a redirect on the port 80 vhost pointed at the https vhost. This is where certificates would likely be configured anyway, so I think this is a reasonable way to do it.
I've been playing with setting up a web server farm, with a fail-over pair of reverse-proxy servers as the front. As a performance measure communication between the proxies and the worker nodes is done over plain http (because I trust my LAN enough for that). I ran into a problem with my tests though where a web app forced https in the software, it produced a redirect loop, because the worker would respond with a http meta redirect to the https port but the web browser was already using that port. Luckly I would turn off that feature in the software.
I understand that forcing https in the software is a good security measure. I'm just asking that it be controlled by a system preference, or be made an optional section in the apache config file in consideration of those who would like to avoid the overhead added by https.