Since we will be after level 33 mods I think it's quicker to farm for them (easy) or buy them. That's why I am making a vendor round today. Per build otherwise it becomes quite expensive. So a build a day I suppose with Friday being 4 days away. I will miss the high rpm on the M4; it will be either mag size or rpm, never again both.
Replacing all mods will be most time consuming and messy with so many. Difficult to keep track of.