Adding this rep sys won't hurt the forum. But I don't support in adding this because as LeGGGeNNdA also said there are many noob who are greedy. Seriously, I'm having such experiences on SAMP forum. Or else after adding it, you can see such:
"My new work...blabla... if u lik diz plz rep meh." or PMs "Hey brother, how are you? You're actually a good person, the great king! Care to rep me?" blabla full of bull ****!
On the other way, your idea is great and I support it. But what to do with those people who are greedy for reps? (I'm not able to give -1 or +1 for this. Good luck anyway.)
That is why i made comment in this topic....I have also a lot of time in samp forums and i see people who make topics with subject "My first FS, Rep+"