but it seems it's a totally different type of tx to what the OP would be sending simply because it has no inputs.
Right, this is a coinbase transaction. But to my knowledge, the same specification applies to these transactions, except that coinbase output must be == to the block reward + all tx fees in the block. Based on this assumption, (and since it is possible to have many recipients in a standard tx as well), I think it is more likely that this also applies to a standard tx.
Bitcoin spec also does not mention any limits on tx outputs :
https://en.bitcoin.it/wiki/Protocol_specification#txBut yet, unless someone can confirm, a concrete test would provide a real answer (and would only cost time).