I can't resist starting with "why not just sign up all your work mates to rugbycomp?"

You might even be able to convince Pdeb to add some of the features to Rugbycomp if they are good ones.
Of course I am more guilty that most of wanting to do things a bit different so I fully understand your desires Tesrof, so here's a few ideas off the top of my head.
1) Pick a few of the interesting TAB betting options. Such as, first try scorer, half time score. A bit of work to calculate obviously as you need to find the relevant data but if you are going to be entering the scores then you can look up that sort of stuff too.
2) Some sort of bonus points if you choose to pick against your favourite team and get it right. I know personally I really struggle to pick someone other than Canterbury, the Crusaders or the ABs to win in matches involving those teams, but often it's not the smart choice.
So you would need to get people to nominate their fav team at the start, and look for people who pick Northland or another minnow just because it will mean they can consistantly pick against them and cream the bonuses!
3) Some sort of multiplier for picking a string of winners in a row for a given weekend.
4) If you are just playing for bragging rights then consider adding a prize pool, even a small one. It's amazing how much more competitive people will be if there is something to win.
That's a start at least, let us know how you get on, but I would seriously consider just using rugbycomp.

Jules