Suggestions for std_srvs

I agree with nearly all (maybe all?) of what @asmodehn said. The more well-defined a node’s interface is, the easier it is to do the useful things mentioned.

But, there are two potential problems. The first is that I think that there is a risk of going so far that we duplicate existing solutions (such as OMG’s IDL). Even if we fix the problems with a system such as IDL, the chance of introducing new ones of our own is high. The second is that such features would possibly be quite heavy.