Even HAL won't find it all that difficult once production gets streamlined. Initially, there will a few teething problems regarding interchangeability of body parts owing to niggles in jigs and fixtures. Plus, a few dimensions may have to be changed on some components owing to glitches uncovered by the Squadron at Sulur. Once that's resolved, given the modern facility that they've inaugurated for the Tejas assembly, it won't be a problem to ramp up production.
HAL's Nasik facility, which assembles Su 30 MKIs, is indeed churning out 16 aircraft per year.