I decided on a new "Feather, the Redeemed" approach. This brew does not pump creatures with shitty spells that generate draw like in Boros. This brew simply uses the best target creature spells money can buy from gruul. So we ended up somewhere in Naya. Even if the opponent kills all 4 copies of Feather, the Redeemed then this deck could still be descent. This because the essence of this deck seems proliferate with a splash of reocurring spell-abuse, what was my goal to begin with.

In a nutshell

• 6 manacreatures to ramp up and "incubation druid" will give us alot more mana to abuse the passive of "Feather, the Redeemed";
• The 11 instants/sorceries offer: Counters, powerboost, firststrike, trample, removal, lifegain (theoretically multiple times per turn);
• Some copies of "Vivien, Champion of the Wilds" grants this deck reliable semi-draw early on;
• Ajani grants extra lifegain and ofcourse more counters;
• Mowu is our hardhitter with trample and vigilance. Put a counter on him asap;
• "Shalai, Voice of Plenty" grants a little bit more protection and can generate counters.

MTG on curve calculator evaluation seems descent.

Sidedeck

• Gaea's blessing against milldecks;
• Return to nature against shitty jankcards;
• Vivien's arkbow against esper control;
• Gideon Blackblade if you need a tank and it combines well with collusus;
• Tibalt against lifegain decks;
• Huatli for more reliable draw but later not sooner (a hard choice between all planeswalkers with drawcapabilities);
• 2 god-eternals for more punch;
• "Finale of Devistation" to fetch that 1 creature that can turn the tide.

Evaluation after 25 games played (5th of May 2019)

List per game, colour, remarks (imgur link)

Won 13, Lost 12, an opponent dq-ed 2 times. I had 6 games (22% of the games) where I made errors which helped me lose those games. So alot of room for improvement!

Lessons learned (5th of May 2019)

• Incubation druid is not as good as paradise druid in a tricolor deck with insanely high 3 manasource demands like "Feather, the Redeemed". Casting Feather early is actually doable with paradise druid and imho stable enough;
• Try to only use instants and sorceries when "Feather, the redeemed" is on the board, else not;
• "Feather, the Redeemed" combines extremely well with "Collision // Colossus", "Domri's Ambush", "Thrash // Threat" is my experience. Every turn you can kill 2 or 3 creatures and planeswalkers, depending on how many mana you have available. After which a Feather +7/+6 with trample can attack, therefore the combopotential is bonkers. Boris instants and sorceries feel really lackluster in comparison;
• First strike is important to have against deathtouch in a creature focussed deck. In a Poliferate deck I would stick with "Battlefield Promotion" but in other deckthemes I will opt for Sure Strike;
• I did not have enough draw early, or I had too many mana-creatures because my hand was emptied very fast. Maybe replacing "Ajani, the Greathearted" by another copy of "Vivien, Champion of the Wilds" is a quickfix to get a little bit more reliable draw early on.

Way forward (after the 5th of May 2019)

Future deck improvements:

• To get a little bit more optimized regarding the ability proliferate. I do not have alot of experience with proliferate so I will investigate proliferatedecks and see where I can improve this deck;
• It could use more reliable early draw. Maybe a mix of cards between "Vivien, Champion of the Wilds" and Rogue's Gloves ,  3 or 4 cards in total. "Huatli, Radiant Champion" emblem is absolutely bonkers ofcourse, but it is not reliable draw and certainly not early enough;
• Maybe cut the 2 llanowar elves depending on how much draw we can generate in a descent Naya proliferate deck;

Upcomming deckidea's with the feather-gruul combo:

The combination of "Feather, the Redeemed" and those 3 awesome gruulspells is absolutely bonkers. It is worth it to investigate the potential of this combo further. So I made a deck for Gruul Stomp in Naya with heavy hitters like Raze-Boar, Forerunner & Ghalta. I hope to experience that having some huge creatures increases the value of the 3 awesome gruulspells and therefore the total effectiveness of the deck and the feather-gruul combo's. The weakness of gruul seems deathtouch so I will add Sure Strike instead of "Battlefield Promotion" in the stompdeck. After that experience I will make up my mind if proliferate is a more efficient way to go forward (or not).

Update (after the 7th May 2019)

I used the Profilerate deck 5/1 brewed by Crasychimp as a template for another Naya deck with Feather and gruul spells. After 25 games I basically got the same results and winrate. Gruul proliferate as a theme in naya feels lackluster in combination with feather+gruul spells. Proliferate is nice if every card adds something to the proliferate theme else it sux.

After these results I also tested a Naya Stomp deck with the same Feather+gruul spells combo in combination with Razeboar and three >7 drop creatures. After 25 games I achieved a 68% winrate and had 2 misplays (without misplays I could have achieved 78% winrate). I want to make the deck a little bit faster by replacing the >7drop creatures and add some lifegain early. This because against monored pelleka wurm does not have enough impact to change the game. Hopefully these 2 chances will improve the pace and efficiency against mono-decks and red in general, I want a reliable brew to take into ranked and test it there. Once the deck is finished, i'll post it on aetherhub in a seperate post.