Strictly speaking, there is no connection between the number of circuits and the "size" of the panel.
Do your calculations...square footage, known loads, etc. Compare this to the size of the breaker; do you need more? If so, run new feeders and replace with a larger breaker
Another approach is to turn everything on, and see how many amps are drawn.
There are two major problems with store-front remodels. The first is the mapping and identification of all circuits. Panel directories tend to be inaccurate after a few tenants.
The other major problem is having circuits cross between different spaces. These circuits tend to continue to "cross over" long after the spaces are re-divided. It is in everybody's interest that this situation be avoided.
