this was indeed my first idea to cut out the old floor and replace it with 2 or 3 sheets of plywood and put some steel sheets under the legs so it would be stable, but since the price on concrete is so cheep I thought I would ask if its as simple as mix / pour / happy, but based on John's response I will definitely not consider it. The other option is to put the a larger steel plate straight on the wooden floor. I think that would also be a good option since this wood is pretty solid, not this new mdf laminte sheets, but probably will end up cutting it up anyways just to see whats underneath and rebuilt it to be stronger. Thanks a lot for all the suggestions!
