Well it's time to start thinking the Mac way. Windows is an inefficient OS and uses RAM similarly. Linux and Unix based OS' do a much better job and for MOST cases, will do a much better job with less RAM than Windows.
Now, there are definitely workflows (think image, video editing, 3D graphics or heavy development) where having more than 4GB of RAM is useful. But if that was your workflow, then the MBA is the wrong machine for it. The MBA is one step above an iPad from a performance perspective so it's best suited for browsing the web, writing documents, listening to music and things as such.
You swapping your SSD out is only giving you more storage, not more speed which you already have with the current SSD.
If you think storage is going to be an issue, you should consider grabbing a larger (say 1TB) external SSD drive and leave the internal drive only for the OS and applications.