While Unity3D may not be an ideal platform, it has some advantages over building the app in ObjectiveC. (https://github.com/realityeditor/realityeditor-ios)
The main benefit is cross platform builds for wearable devices in addition to android. Wearable devices (ex. HoloLens) are becoming more and more important in AR, and seem to work well with the Reality Editor concept. However there are many competing wearable manufacturers with their own development pipelines, and ObjectiveC limits the app to iOS devices. Unity3D offers “write once, run most places” with C# compiling for most platforms.
The I do not think the web technology foundation does not need to be sacrificed in a Unity3D based client. All currently available features and design decisions seem to be possible to implement. Yes, a Unity3D client will be more “bloated” than one written from scratch without an engine around it, however it offers additional flexibility that may outweigh the drawbacks.
Please let me know what you think,