If you pick a base character then the prime gets removed as well, the better version cant exist without the base version, however if you remove a prime version then the base character can still exist. My personal pick would be Valkyr due to how [IMO] useless she seems
She’s not that bad though. She got some changes that made a ‘pounce’ build worthwhile, if a bit slow (using her 1, 2, and 4). It could use a smidgen of a boost to really excel but it’s a decent option overall. You slap roar over her 3rd and prime with her 2, and you can easily hit 4 million damage from a single strike of her 4 (so I recommend range so you hit more enemies instead).
She’s not like Frost who needs all of his augments integrated or Chroma who’s a dragon without the dragon part, both frames ‘taking up the theme’ and being DE’s excuse to not have a better frame/kit designed for a dragon/ice themed frame.