I've done this one a few times, it was the first way I managed to win. It can be done without firing, punching, or infact ever being seen.
For easy 'velvet' mode then use the liberal guardian and a stealthy individual to steal stuff for them to run in special editions. You can generally win the game within around 4 years using only 2 characters, thief and writer. And the only reason it takes that long is the usual entrenched politicians.
For a harder 'velvet' I prohibit myself from building a guardian. Victory here is still surprisingly easy and often faster than a violent route. Stealth is great, just rob a load of sites blind, even if you strip the site completely and leave with them only suspicious they seem to suspect you and the papers credit you.
The reason I find the non-violent route so absurdly easy is that you can steal every single last loot item at a site (and interact with all machines/etc) and as long as you didnt do any shooting then the site will not close down. As you may already know, leaving a site on high security rather than closed down has a larger impact on opinion.
The only 'velvet' that busts my balls is velvet from nightmare. You pull that one off you let me know
Technically its no harder than from regular start if you are being non-violent, but you dont get to make any mistakes, generally my thief will make at least 2 trips to the courts before i win (he defends himself, nobody in my organisations is ever below 4 law), in a nightmare mode you may not have that option if you didnt manage to dislodge the deathsquads yet. Nightmare starts also rule out activities like graffiti and disobediance untill midgame (unless you like to run from DSquad). For velvet from nightmare i really must highly recommend focusing the courthouse and police station asap until the DSquad vanishes