I feel your pain. My town used to have a lovely indoor gym inside of a much larger sports club. Unfortunately, the club removed it to make more room for yoga. I thought about building my own gym as I have 11' ceilings in my garage but I concluded that the time and money would be better spent on gas and a gym membership. (I've worked as a carpenter and have built a commercial climbing gym).
You specifically mentioned wanting to get strong for technical trad routes which means getting good at crack climbing. Even with your limited ceiling height, you could conceivably build a 'crack machine' that would offer a good workout. A crack machine could be as simple as two 2" x6" studs attached to an existing wall or as complicated as an adjustable angle wall, from vertical to overhanging with an adjustable width crack. Or, you could build a wider wall with several permanent cracks of varying sizes. The upshot is you can practice everything from thin fingers, off fingers, off hands, hands, fists, to off width sized cracks. When you can easily run laps on all the sizes, you can make it harder by adjusting the angle.
Google crack machine and you will get a number of 'how to' articles. This is a decent one from Rock and Ice:
http://www.rockandice.com/climbing-news ... ing-system