Well, the other solution is to abandon your
for
boots instead. The 10% MS on Runic Echo more than compensate the 20 Flat MS from Swiftness. With just your 345 base MS, you already gain 14 MS compared to the old build. Factor in that the %MS is also applied to the boots+enchant and you are really faster than before, even without Swiftness. Plus you get 10% CDR on your Summoners as a bonus, and 20 more AP for your ratios.
IMHO, the real nerf for your build is that you will proc Echo less than Spellblade, and the ratio is lower. I guess it was very possible to proc Spellblade on all of Q/E/R, if you payed attention to the cooldown on Runeglaive? Now, it will be good if you manage to get 2 Echo procs in a given fight. That's like a 60% AP nerf.
And there isn't really room for a Lichbane in your build, unless you're ready to drop the sustain from WotA.
Anyway, it's a fun build :) I wonder if you could fit a
in here somewhere? Instead of Nashor's, maybe?