No comma！ Only in this way can you hope to make improvements in the operating system.

Yes, inversion IS needed in your example and there should be NO comma after "only in this way". Please learn the following rule: Subject-Auxiliary Inversion is needed whenever a sentence starts with a phrase that 1) is NOT the subject, 2) contains a NEGATIVE word ("Never", "NOwhere", "by NO means", "under/in NO circumstances", etc.) or a limiting word (e.g., "hardly", "barely", "rarely", "seldom", ... "ONLY".... , as in your example), and 3) is NOT separated by comma. Hence, you may say " I had never in my life felt so embarrassed" (no inversion) or "Never in my life had I felt so embarrassed" ("Never" in focus, inversion), but not "*Never in my life I had felt so embarrassed"; similarly you must invert in "Nowhere else could I have afforded to buy a house", "By no means did I intend to offend you", "Under no circumstances should reference books be borrowed except on week-ends", "Seldom had the stockmarkets plummeted as they did yesterday", etc. As to the role of the comma, its presence makes inversion impossible in many other cases, cf. "In London, most people can't go to work in their private cars any more" is OK, but "*In London, can´t most people go to work in their private cars" is ungrammatical. Also, compare "Under the church, there is an old Saxon cemetery" (comma, no inversion, OK) with "Under the church is an old Saxon cemetery" (no comma, obligatory inversion), but note that both "*Under the church, is there an old Saxon cemetery" (comma, inversion) and "Under the church a Saxon cemetery is" (no comma, no inversion) are ungrammatical. I hope this really explains to you what happens in this kind of example.