Several languages in which English has its roots have easily definable rules. For example, sticking "a" in front of an adjective can mean the opposite of that adjective (symmetrical - asymmetrical), while you can accomplish the same thing with "dis" (satisfied - dissatisfied). Similarly, suffixes can be tacked onto other words to create new words (for example, turning beautiful, an adjective, into beautify, a verb). These patterns are quite obviously present through our language, and are powerful tools to create new words that may not be officially recognized as part of the language (e.g. documented by Webster or OED).
If one were to use these rules to create words (uglify comes to mind, being the opposite of beautify), would these words be considered proper English, or have we dropped the suffixing/prefixing rules of our mother languages, and such words are no longer acceptable?