hashtagchanMetalworks: voted out by 50% of Prem, the map everyone loves to hate.
Sunshine: vicious response from EU after the One Night Cup
Glassworks: far too large from our playtests, definitely a contender for HL though.
Sandstone: not reached pro yet, will definitely have a look when Fantasmos releases that version.
Intermodal: didn't fare well in any of our doublemixes, as well as HL hate.
Grizzly: didn't fare well in any of our doublemixes.
Convolve: textureless, appears to have been abandoned, was actually a lot of fun.
Metalworks was taken out, and it wasn't right for it been taken out, since it was a great map, which look for example in the NA scene, it survived for couple seasons already, it only needed proper feedback to Scorpio so he could've altered it to make so it can be tested out a bit more.
Sunshine did not receive any vicious response, it got constructive response when we suggested the map maker changes that were needed in order to make it more fluent and playable, it was dropped by ETF2L however for some unknown reason, from my perspective after playing the map all the way to the finals, it felt very good, even though it was before Deer improved it.
Sandstone looks great, but it needs players to play so the final pro version would come out finally, the map maker won't just make changes on his own mind, he needs people to give feedback on it so he can finally release it so bringing it to the cup would make great sense.
Glassworks looks kinda nice, yet nobody ever made a move to give it a go, since it was never really tested I can't give my opinion on it.
Intermodal is more of an HL map than a 6's, after playtesting it somewhat.
Grizzly, never played it, can't give my opinion on it.
Convolve didn't receive much of a playtest so I can't give my opinion on that matter.
However, since you've clearly looked at some of the new maps I'll give you a couple more to consider:
koth_airfield, a very popular 4's map (yes I know, 4's isn't serious or w/e, but it was still really popular there) but this map has potential, and never got recognized as a legitimate possible 6's map.
cp_ediface, many people wished for the return of famous cp_gravelpit, yet nobody really gave this map a shot, only UGC in their pre-season week iirc, therefore playtesting this would also mean something, not many people love A/D on 6's, but this map deserves a shot.