I find Googles really useful to check vailidity of transactions and already mentioned in our Java SDK thread that you should consider providing an API for that. In my opinion - if not too expensive - it would be really useful to have that validity check provided through the core API (maybe only in debug mode) because the network_id can always differ and Googles can actually only be used to check the validity of mainnet transactions.
Of course it could be cloned and adapted to point to the local network. But what’s your opinion about that?