if a newly infected HIV+ individual chose to start treatment immediately, and stopped treatment a year later, what physical effects might he expect to experience?

In the situation you describe I would expect that most people would experience little or no physical effects from starting and then stoppin therapy. Some might experience side effects associated with their antiretroviral therapy, but this would vary depending upon what medications are used and would differ from person to person. A small number of individuals can experience an acute "flu" like illness upon stopping therapy, but most will just have an increase in viral load associated with no new symptoms.

I hope the above at least in part addresses your question. Best, Eric