@Kruti Shah - You can consider the following points while introducing a uniform pay revision cycle.
1. Cut Off / Eligibility Date should be at least 6 months or more from the date of Pay Revision. So the employee should have either joined before 6 months or their last salary revision should have been minimum 6 months gap. Keeping a 6 month gap will allow you to measure performance, and would also justify the need for salary revision.
2. Those who are left out because of this criteria - should be covered in the next cycle - initially do it every 6 months - for 1 cycle, and then they can be moved to the annual cycle.
3. Make the payments on a pro rate basis. So if the average hike that you are proposing is 12%, then if someone has joined before 8 months or has completed 8 months post his last salary revision date - give him / her a 8% hike.
Feel free to connect with me in case you need any more info.