It's true that part of why we didn't go forward with one of the various "thread-attachment" ults (even though they were very cool and a slam dunk on the thematic) is because they were very heavy on cc and pushed Gwen away from the skirmisher space, but there were also other reasons.
The coolest version in my opinion, which is the one shown in the gif in this article, also had an issue where it needed Gwen to input multiple different directional commands back-to-back which didn't fit well with the base kit which already asks you to do that (both Q and E are high-frequency directional casts that are often cast on different vectors). So while it was super fun to use in isolation, it was very demanding of the player to manage casting Q + E + R1 + R2 all in a short timeframe given they were typically all in different directions and some required high precision (mostly the R casts). One of the big advantages of the final ultimate, even though it has three casts instead of two, is that it (generally) shares a cast vector with Q which requires less cursor repositioning.
This isn't to say we didn't want to make Gwen mechanically complex, but the experience actually playing with the needle-attachment R was poor for most players when optimized, even those used to playing other mechanically intense champions.
I do think this "bind-together" R spell is really cool in isolation and could work on some kits (personally I absolutely loved casting this R), but probably shouldn't be combined with a high-frequency base kit with a lot of other directional inputs.