Reply: A wireless system (one transmitter and one receiver per microphone) weighs at least one pound, so that would not provide a weight advantage. Here's a suggestion. Use thin mic cables (about 1/8" diameter) which weigh much less than thick ones. Run all the mic cables from a conference to an automatic gated mixer (such as the Shure SCM810) under the table. Then run a single mic cable from that mixer to your recorder. Or, you could even feed the output of the mixer to a single transmitter, and pick up its signal with a single receiver that is plugged into your recorder.
You might want to use an infrared transmitter/receiver instead of the usual radio transmitter/receiver. Infrared waves stay inside the conference room (aiding security), but radio waves don't. The Nady IRW-215 is an example of an infrared transmitter/receiver.