Making your own source is not as hard as people make it out to be... All you have to 'get' is packets and sockets really... I mean yes, any source you make with limited understanding beyond those two things is going to be.... less than perfect but it's not THAT difficult to get to the point where you can log in.
That being said making your own source (DOWN THE ROAD, NOT NOW) is a great thing cause you understand where things are and what they do in your source far better than you ever will in a public source. I've found that with my source adding new features or fixing things is a breeze compared to any other source cause I know exactly where to go and what section of code may be causing the problem. Yes, alot of that is due to experience but alot of it has to do with I WROTE THE DAMN STUFF, I should sure as hell know how it works lol..
Hybrids is a great base... but keep in mind that there are no servers to log packets off (other than servers already made by people... most of which are horrible) so you may have a hard time coding a server for a patch that isn't well documented (eg: 5017, 5095, 5165 where like everything ever is known about packets/game systems)
That's another reason why I enjoy going with current tq patch. If I don't have a packet for something, I go log it!
Ps: you may want to check out these links, not cause I'm awesome but cause it was me struggling with alot of the things you will be.
Some mini assignments to try to code:
All my coemu links
Links for information about bots/proxies/packets. You will only need to pay attention to the encryption and packet information/links though
Some rants on certain functions in C# and how to use them/code things
Note... that rant is old so some of my examples are far from perfect.