As you write "table with >30 input columns", I assume the user to spend quite a lot of time editing this table. Tables with 30 columns tend to take up complete screens, so I think the design should change to give InputTable a page of its own. Below, I've written down some thoughts on getting MasterList, MetaData, and InputForm+SomeOtherRegion ouf of the way.
During this time, there is probably no need to look at the master list, or select other master items (which would change the entire contents of SubRegion, I understand). So when the user starts editing the input table, the master list can (and should) be moved off the screen. Depending on the the other stuff in SubRegion, you can even think about a full-page master list and a full-page SubRegion. If this is not feasible (because the user needs to switch master items while looking at InputForm and SomeOtherRegion), I would consider moving the InputTable to another full page.
Similarly, I would also move the MetaData out of the way. It takes horizontal space from the 30 columns, which will already be cramped on a regular screen without the MetaData pane. If the user needs to see MetaData while editing the InputTable, you might put them both onto an own page. Maybe the MetaData is shown on this page, and there's a link to navigate to the MetaData+InputTable page?
As you did not write anything about the number of rows in the InputTable, I assume there are only few (because the table is not tall in your design). If that assumption is wrong, you need to make vertical space by either collapsing SomeOtherRegion and InputForm, or by moving the InputTable to a page of its own.