It's true that riders coming from 2nd division have low salaries, but I think that those riders either they are young and they are not going to win as much as the experienced riders, or they come riding for teams that are likely going to be relegated again. Of course there will be some exceptions, but all of the participants are free to pick them so everyone is equal.
About the own team +1 star sounds also like a good idea, but gives you a disadvantage if you have more than one top rider in your team, someone that everybody else is going to pick.
I would say just try it rough next season, with no restrictions from your team/teams coming from 2nd division, see how it goes, and then restrictions for the following season.
About the stars, what about:
1 star: not more than 860
2 stars: not more than 1500
3 stars: not more than 4000
4 stars: not more than 8000
5 stars: 8000+
Any way to see a list of riders sorted by salary in game?