There are 3 levels of remodelling. Each remodelling level requires you to max out the level first and also costs cores and memory fragments that you get from the new(ish) frag simulation. There are currently only 6 characters that have a remodel and it requires you to invest a lot of time to do it for each character, especially for the 2 four stars characters (M4A1 and AR-15).
Silvermarch said: ...especially for the 2 four stars characters (M4A1 and AR-15).
He ain't kidding. MOD 1 is easy, just grind to lvl 100. MOD 2 is reach lvl 105. MOD 3, reach lvl 110, is such a steep spike in exp requirement. It feels like the time it takes to get an extra level has doubled.