There is a document form 1158 where the name "forum apud Munichen" appears, which means "market/forum at the monks". So, "Munichen" is dativ plural of the Old High German word munih which means monk in English.
In German Munichen lost the i between n and ch, and u turned into ü, so we have today München. The i disappeared, because for German native speakers Munchen/München is easyer to pronounce than Munichen/Münichen. München comes smooth over the lips, while Munichen feels a little bit bumpy (maybe because it has one syllable more than München).
According to your theory München should be harder to pronounce than Munichen, but the development form Munichen to München confirmes, that the opposite is true.
So, the idea to insert an extra i in words, where ch is the second (or even third) part of a consonant cluster, seems very far-fetched to German native speakers. We German native speakers love consonant clusters, and German has lots of them. In German there is a word that contains of just one syllable, but it has 7 different sounds, only one of them a vowel, and we are very happy with it:
- Strumpf [ʃtʁʊmp͡f] (engl: stocking, sock)
Other examples are: spritzt [ʃpʁɪt͡st] and springt [ʃpʁɪŋt]
There is even the word Gstanzl [ˈkʃtant͡sl̩] (some kind of Bavarian or Austrian folk song) which has 8 sounds, 7 of them being consonants.