If you pick any map starting with CTF_ you'll be playing capture the flag, it's already in.

Here's a link with a filter that shows you all the capture the flag maps: http://psteamcommunity.yuanyoumao.com/workshop/browse/?appid=520010&requiredtags[]=redflag
(You might have to copy the link, formatting is making it not work properly...)

Shoving people is a hard problem, because network lag makes the shoving action lag behind the reaction to it, and moving people without them controlling it or being able to anticipate it is likely to cause motion sickness.