I don't think there's a KE benefit to having CA-215 over the retrofit. Hitting 1700 CE is more important, because you're in semi effective range. Going from 1700 to 1750 makes a huge jump in defense compared to 1650 to 1700, because the semi effective range for most battle rifles (2200 CE) starts at 1689 and ends at 2036 when you start actually blocking some of them.
So for CE, every point between 1700 and 2036 matters way more than every point between 1450 and 1700.
For KE, there are few weapons that hit over 1505 that are worth blocking, and 1505 is the end of the semi effective range to cover most KE weapons.
Explained more generally, the breaking points for most defenses where there is a chasm between this and heavy hitting weapons (sniper rifles, laser rifles, etc.) are:
Beyond these benchmarks, there are almost not benefits to increasing defense, increase AP instead.
Below these benchmarks, you are crippling yourself to most powerful weapons.
Between those two bounds, are semi effective ranges, where your marginal damage taken per hit is much lower for every added point of defense.
Semi effective ranges go from 1.3 times below the defense, up to the defense. In THESE ranges, you get a huge benefit for increasing your defense, but not as much as you would if you reach the benchmarks. Once you hit as many benchmarks as you can, then you spend your extra "defense points" maximizing within these ranges:
1505 - 1900 KE (everything is semi effective here, so it's an even trade between lower and upper bounds)
1692 - 2200 CE (There are no semi effective benefits between 1111 and 1692, and no effective benefits)
1152 - 1500 TE (Again, no semi effective benefits between 833 and 1152, but there ARE effective benefits between 833 and 1200)
Since CE has no effective or semi effective benefits between 1111 and 1692, in almost all cases, you can improve defense elsewhere. This means that 1700 KE, 1111 CE, and 2000 TE is far superior to 1500 KE, 1400 CE, and 2000 TE, even though the second set adds up to a higher value.
That's because your gain between 1111 CE and 1689 Ce, while 500 defense points, affects your general survivability less than adding an extra 200 KE, which is in the semi effective range, giving you much better defenses on average.
So I would suggest aiming more for 1700 KE, and if you can't hit that, maximizing AP/stability/mobility instead of defenses.
Now obviously there's some metagame effect where, if you know your opponent is running battle rifles and no KE weapons, you can get more of a benefit by keeping KE low to keep CE high... but that doesn't necessarily mean much unless you know in advance what weapons your opponent is running.