The answer to your question is No, in order to set the composer you needn't reinstall InDesign. The World composers are needed for other languages than the Middle-Eastern ones as well, such as the South-East Asian languages. And it works fine for English too.
To get access to ME features there's no need to reinstall InDesign, a simple tweak exposes the ME menus:
https://github.com/jackweekes/InDesign-Feature-Set-Locale-Switcher
Furthermore, the ME (and Japanese) features are exposed to scripting, so you could even use the standard non-ME InDesign and use some scripts to set Right-to-Left features. Soe of these scripts are simple one-liners. Look around on the web for them.
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