I know its a long title, but let me explain a few scenarios whee this would be great.
A client needs to analyze some data and possibly even run some manipulations on it. Maybe even store different iterations of each scenarios. Based on data that exists on a hosted system. Now imagine if you wish they have loaded all this into a local table. These tables could only be create, updated and deleted locally - they have no connection to the server. It is for the user to perform these scenarios. They might even get on a plane plane and continue to research the data.
In a sense Tableau is like that. Once you have extracted the data you can work disconnected from the data source to explore and gain insights from your data.
Back to my scenario example. Imagine running a script to load the data you need to work with and it not only loads the data but it actually would allow you to create the tables and load the data.
Now you can be offline working and running scripts to manipulate the data maybe even creating even more local tables. Saving each of those scenarios etc. Then you get reconnected and its time to send the boss your analysis... so you take a table and with some new and cool new scripting features - there would be a simple way to transpose the records you created to the server now that you are reconnected.
It could also allow for another pattern that we use.
Lets say a user wants to create a new widget. We have a way for the user to fill out some global fields show those in a card window. That is nice. But sometimes the user could start entering some data and they have to wait before completing that entry, because the user has to pull out some identification. What if in another window you could kick off another data entry screen. Right now if they were globals you would have cross talk. You would see the original globals and overwrite them. Then you could manage reaping globules but that gets messy, to say the least.
But what if you could create local schema and have a flag that says you don't want this schema to live on the server. It only lives for this user locally.
Now in the last example, staring an entry and adding a new one would simply be a new record. Then when you submit it to the server you could perform whatever validations you need and delete the local record. For that matter delete the entire local tables. Anyway they belong to the user so it doesn't matter.
This would give us an extreme amount of flexibility. No network traffic because all these things happen locally. And maybe all these tables are all in memory.
Not sure how one would style something that doesn't exist or for that matter attach script or script triggers... save that for another discussion. I am sure there are many other considerations like security etc. Again for a later point.
Maybe a better name for this suggestion would be local schema. Anyway. There it is.