In my opinion this must not be clubbed or introduced as an alternate to payment of "(statutory) bonus". Some companies pay Bonus to employees even if they exceed the statututory limit (of Rs.10,000 salary).
Now, bringing a new system of "loyalty" Bonus is something a different approach to keep an employee for a long time. By introducing or proposing to introduce this system will not yield any big results.
I have introduced a loyalty Bonus system, have a look at it.
12th November 2012 From India, Madras
14th November 2012 From India, Pune