Recently Wizard of the Coast started releasing optional additions to 5e classes along with full revision of ranger class (he was too weak) on theirs site in sections called unearthed arcana. These options are not final and official yet but subject to playtest and discuss for the moment *. Due to the fact that lifetime of characters on the show isn’t particularly long and thanks to setting they can be easily swapped for another character, it is perfect ground to play around with these options.
You can check these out on http://dnd.wizards.com/articles/unearthed-arcana
Ranger revision is here http://media.wizards.com/2016/dnd/downloads/UA_RevisedRanger.pdf
+2 dmg on construct would help Day9 (technically he couldn’t get it until lvl 6 but + on humanoids would be awesome too) , also another ranger conclave dealing with underground would fit his character nicely, also beast mastery doesn’t suck apparently anymore since there is no need to forgo an attack. There also sick buffs to initiative and movement through difficult terrain, all around good stuff 
*Not Ranger though, they want to release it with the next core book, maybe with some small changes
I forgot to even mention why it would benefit players and campaign and that is Options are great. They allow wider range of characters and classes to be seen, allowing players to take interest and experiment some more. For example party needs a tank? maybe a kensei monk then, whilist not fully defensive it fulfills the role. Want to play paladin but it doesnt fit the party? Then treachery paladin fits right in Yours loving murder hobo deceitful party. Party needs a healer and being just a healbot cleric isnt fun? then pick druid or a monk to be very UNIQUE class that which can offheal without wasting spells slots or actions to do so. There are even new weapon traits which may be helpful and flavorful soon, since lvl 4 is not far away.
Even if Adam wouldn’t allow these extra paths i think that ranger revised version should be in the next episode of the show, rangers are fairly weak in my opinion and day9 needs all the help he can get. So now i raise a question to You community, what are Yours thoughts about all of that? And would You like to see it in the show. Also im open to discuss and speculate on specific paths in unearthed arcana section of the wizards site.