Your solution addresses the effects caused by server imbalance by giving arbitrary bonuses to the "weaker" side. To truly fix the problem you have to tackle the cause not the symptoms. The cause is more people are rolling empire than republic.
Static bonuses would mean in warzones and solo encounters the underplayed side would dominate. So cruel and capricious players in the system you envision would role Jedi shadows and scoundrels and mercilessly stalk and grief people in world pvp relying on said buffs to keep them from ever facing a true source of danger.
So obviously your proposed stat buffs could only be important in non instanced objective based group pvp where one side consistently is under represented. And considering that there is only a singular zone that fits this criteria ,Ilum, your proposal does very much mirror the tenacity system of WoW’s wintergrasp which ultimately was replaced with an instanced zone that limited the number of people who could play due to the fact that such stat bonuses do little to actually mitigate even the symptoms of server balance let alone the cause.
You also suggested that item and gold drops should increase on the side receiving the short end of the server population stick since stuff on that side of the server costs more. Assuming that economic manipulation of faction based server was so easy that such simplistic approach would work the consequences of it would be a great boon for gold sellers/farmers. By farming gold and items on the minority faction their time and effort would be doubled nay tripled by transferring though neutral auctions the fruits of labor to markets where there are2 to 3 times more prospective buyers.
The fact that it is harder to get groups for operations and flash points for players on the minority side is true. But saying that those players should get bonus loot and have an easier time running the instances is bordering on asinine. Think about it in reverse. If your faction has more people than others we are going to give your bosses 10% more dps, health and half the time they won’t drop loot. Why does it matter going into an instance if your side has fewer players than the others you can only bring 8 of them.
Aions hard system of preventing character creation of high population factions has its own issues but it actually addresses the root cause. If you’re going to just treat the symptom do so by making new content non faction specific. Such as more warzones like huttbal for those pvpers on the majority side or flash points that force sith and jedi to work together to overcome a an instance together. I personally would like to see more pvp that was not faction specific but think that instance idea is almost as horrible as your stat/exp/gold boost idea.
TL:DR Your idea is only a bandaid not a cure for the actual problem server imbalance. And it’s a highly flawed one