I agree. While it would be suitable as a weapon, I think there are better avenues to explore for energy sources. I had made the suggestion of using an RTG, or Radio-isotope Thermal Generator a while back. I still think it would be pretty cool.
An RTG produces electrical current based off of the Seebeck thermalelectric effect. Basically it takes two units, coupled together, that have radically different thermal states. The excitation due to thermal energy of one unit creates pressure which then flows to the other unit, generating current.
See the following link:
http://www.wws.princeton.edu/cgi-bin/byteserv.prl/~ota/disk1/1994/9423/942306.PDF
While the RTGs discussed weigh approximately 1-2 tons, they also produce anywhere from 9-20 Watts constantly for at least a 30 year lifespan. If these generators could be scaled down for uses in the armor I think they would make an effective power source.
See, the community has developed this carbon fiber nanotubing that acts like muscle. When you apply an electric current to it it contracts and then relaxes when current is removed. But it's 100 times as powerful as muscle, approximately, per similar densities.
http://www.eikos.com/articles/carbnano_routetoapp.pdf
(This is a lengthy article but discusses a number of applications for this material. Look under Electromechanical Devices, it's in the second half of this section.)
The generators would provide the current needed to drive the nano tubing throughout an armored exoskeleton. These methods would eliminate a lot of moving parts making the suit pretty reliable for away missions and with such an efficient power source you include a number of other tools.
The suit itself would have to be as lightweight as possible. I would suggest components of Liquidmetal Steel and Tungsten alloyed or Ceramic Aluminum composite. This would provide a very strong, very corrosion resistant, light weight, and heat resistant material with which to craft the armor. Any heat generated could be fed back into the RTG to improve efficiency.
http://www.liquidmetal.com
http://www.astromet.com/alumina-ceramic-amalox68.htm
Right now I can't decide between the steel or the alumina. I wanted to bounce these ideas off of the posters here as a lot of good knowledge is being thrown around here.