I lease several commercial properties.
My typical lease is 2-3 years upfront with a pretermined option for a few 1 year renewals. All of my leases readjust annually and are tied to the CPI and read as follows:
"The base rent shall be adjusted as of date by applying a cost of living adjustment which cost of living adjustment shall be adjusted thereafter every year.
The cost of living adjustment shall be determined by measuring the percent change, if any, in the Consumer Price Index (defined as: Consumer Price Index for all urban consumers, all items, Midwest Selected Metropolitan Areas, Midwest Region with a size population of less than 50,000), provided that said increase, if any, shall not exceed 6% in any one year period."
Works for me and the tenants also.
You might want to consider amortizing a percentage of the leasehold improvements over the first 3-5 years of the lease via a rent reduction.
Hope this helps