Honestly, I'm not so sure why everone is freaking out about Tarkatan. Acidic was already better, but those of us who went with Tarkatan would be fools to think that the rekkas would stay the way they were especially after Tanya's rekka nerf. First of all, if you were expecting them to stay as they were, you were being naive. If you played it smart and realized that the rekkas weren't gonna stay, then you were never using them as your primary block string ender anyway, and instead used your -7 tail flip for a relatively safe ender.
Think like you're playing street fighter. Any Ken or Ryu player can do their target combo into either fireball or dragon punch. This is a hit confirmable option select. On hit, you go for the bigger damage with dp. On block, you go for the block string into fireball for safe pushback.
Alien's 214 is the same thing. It is a hit confirmable option select into either rekka, tail flip, or krawl. On hit, use the rekka into grab ender. On block, use the tail flip for a safe ener.
Alien still has good 50/50's. Once you condition someone to respect the overhead tail flip, you can start playing 50/50 games. At this point your opponent, knowing you won't be doing rekkas on block, will block low, which gives you an opportunity for F4 into rekkas. If you see them block high, b3 into rekkas.
Every successful knockdown should result either a meaty setup or a bait. The meaty setup of F13 can be option selected into either rekkas on hit or tail flip on block. If you're not going for the meaty, you should be going for a bait. If you bait the move you want, punish accordingly. If they simply block, you have your 50/50 f4 or b3 on reaction.
Risky, yeah, but rewarding to play. Acidic is still better, but tarkatan is just more fun.