More of a whine than a suggestion, but if there is any manual intervention at all, please try to make at least one of the gates have an arena after basil! There is only one arena and it is at level 10. I enjoy playing the game and the less monotonous nature of the Arcade is good, but having an arena in the second half of tier 2 would seem the best practice to learn the survival nature that is required in tier 3.
Although, I did notice that the recent arena after Basil (2 out of 3 rotation) was abused by a lot of people (myself included, thank you Party Finder) so I understand it can be exploited. And I recognize that there are at least 2 or 3 gates that have a level after Basil that have a chance for a danger room - thank you.

Because I probably need a suggestion in here: Perhaps make one of the tier 2 gates have a persistent Arena on the last level like JK or Twins. An if you want some attention given it maybe have a big something or other (Danger Mission big guy, Trojans, Monster lichen, etc. - preferably of a different monster family!) on the last arena stage in addition to all the robots/gremlins.
Or heck, make it a true practice for tier 3 and allow/make players to "rent" gear from one of your gremlin vendors so they can try out higher * weapons before investing.