Flat Bituminous Roof Leaking - Repair or Replace?

[Dar Fornelli]

Renovating a 4-unit apartment building here in Kansas City. We have an old bituminous roof, not sure how many layers, and have a few active leaks. Flat roof, ~2000 SF. It looks like the main issues are at pipe boots, but there are numerous cracks in the roof and the roof is generally in marginal shape at best. 

We're gutting the entire building, so we're trying to control budget as best we can. Would you repair the roof, add another layer of asphalt, or go full boat with a tear-off and new roof?