Well for a start, I suggest you make your bot a metamod plugin. This way, you won't need to worry about the game entities and you'll let Will Day alone deal with the madness of the Steam compatibility.
In my opinion, it is definitely be possible to port botman's code to OOP, although it's a perilous exercice. I would rather suggest you start writing your own bot, using botman's code to pick ideas from, with a class hierarchy similar to this :
Player (top level)
Bot (as Player::Bot, subclass of Player)
subclasses of Bot (like Bot::BotBrain, for example)
And additional side classes like "Server", "Round", "Mission", etc.
Good luck !
