Playing unleveled mechs, in my experience, doesn't necessarily degrade performance that noticeably. I've been making a habit of tracking some of my mechs as I level them, because I'm a spreadsheet nerd... and some of my mechs performed better without Basics than they performed after I finished Elites. Why? Because other factors have more impact than whether your mech has skills on it or not.
What I actually do is play all of my mechs without leveling them, I just stock pile the XP for 20 matches or so, and then I save my stats. Then I spend all the XP at once, get all the variants Elited in one go, and play 20 more matches again per variant, and compare the before and after. On average, my mechs put out about 62 extra damage after they are elited. It's not a big difference.
Similarly, what builds you play doesn't tend to matter as much as you think they might. For instance, my best performing mech at the moment is a Kitfox (lol, it's doing better than my Kodiaks atm), and you should see some of the potato builds Proton runs in his spare time, and he still tops the charts with those builds, like gauss+AC2+SRM4, and gauss-streaks.
Edited by Tarogato, 02 February 2017 - 07:55 AM.