As we make this offer, should we increase his starting wage beyond
what he has asked (say 5% over 50k)consider we won't be able to give
competitive salary increase annually?
No. While I understand what you are trying to do, it simply won't work.
Once you give a new employee a salary, that will become the anchor for that employee's expectations. If their annual increase is 2% and everyone else in the industry is 5%, they will feel cheated anyway. They won't remember that you attempted to give them a higher base a year ago.
I have no idea why your company would consider it okay to give 5% more than market rate initially, but to consistently give smaller raises than the industry. That makes no sense to me, and virtually ensures that you will lose people.
If it were me, I'd work on getting the annual increase policy changed to more closely align with the market and competitors' practices.