I posed the question about converting non-com translators into commercial ones to someone with more experience than I and his response was: "As long as it is not in the reserved band, yes--as often and as easily as some folks change their underwear (twice a week?)".
The main difference between the two, when operating on the non-reserved part of the band is that non-com licenses pay no regulatory fees, while commercial ones do. This puts non-com applications at risk during filing windows because non-coms cannot pay auction fees either. So, they only acquire channels when no commercial interests are concerned. However, once a translator is granted, converting is as easy as filling out a form and paying the fees. BTW, there's no fee refund if you pay for a commercial license and then take it non-com later. There's also no requirement for a substitute non-com translator to exist in the area.
Though not part of this discussion, one other minor difference exists between reserved band translators and those operating on the non-reserved band. Those in the reserved band (88-92mHz) can be fed by satellite or any other means whereas those on the non-reserved band must be fed from an off-the-air source regardless of their commercial or non-com status.