Although I can't say for sure, by all indications, Lua Plugins will never be able to interact with existing UI elements. At best, we'll be able to override them, but never alter them. The main reason behind this is that the Lua API is a completely separate entity from the UI elements in LotRO itself. Nothing in LotRO is done in Lua, so every function, class or element available in the API had to be created from scratch not only to make use of these things, but also to deliver the information to the API.
So some time in the future we may very well be able to add keybindings to the Lua quickslots, and maybe hide the standard LotRO quickslots, but it's very likely that we'll never actually be able to access/modify those LotRO quickslots through Lua.
To answer your question - the only way to do something like what you're describing is to create a custom set of quickslots, and to save their contents. Saving multiple sets would also be quite possible - and in numerous ways. However, at this time, the only way to use the skills/items in those quickslots would be clicking on them. There's no keybinding support as of yet.