Another option if to use PfR or OER that is routers use active probes or netflow data to select a path dynamically. Or of course the very simple option is to hard code OSPF cost values.  

The other consideration is are you trying to code a static metric or do you want dynamic behavior (latency changes with traffic load).

Finally as was mentioned above, are you sure you want the complexity, if you look at EIGRP it has a load metric but no one ever uses because it adds operational complexity and you can get traffic oscillation.