So you're saying a Create Warforged feat would be required, along with a forge (say of value equal to 2k gp?) and a special ritual for each kind of warforged I'd like to create which happens to include a live darkwood tree?
About the darkwood tree... are they common? I ask only because since Warforged are a PC race then they must be common themselves, even after all the broken or disabled/destroyed ones have been decomissioned. I think that unless this is the case, the designers of the warforged had something else in mind.
The warforged were created via special forges beneath the surface.
It was a mass produced thing, they do not reproduce. They also can't be "turned off" - they are "living" constructs - not merely animated objects. I think that is where you basis is lacking. By starting with a construct you miss a whole lot of what makes them special.