Well, you would need to add support for all of the different features Nxt is implementing, right? That is the only reason I thought it would be more complicated, as Bitcoin/Litecoin Electrum clients don't need to worry about support for an asset exchange, marketplace, etcetra. Then again I am not a developer and you sound like you know a lot more about Nxt than I do. 
I am a developer and do understand how NXT works, even though I haven't looked at its implementation code but mostly at the API.
I can reuse the NRS and MGW Lite UI, so it would be a matter of creating a Proxy that has the same API as the NRS and pass them onto a service API to get the information and perform the functions needed.