Some rule-sets combinations could lead to not having almost anything to submit this is a lot worst in modern that there are less options, fortunately it does not happens so often.
Can be see on the image: Only monsters with Odd mana cost , Only Range units, no Neutrals only Life and Dragon 12 mana cost, my only option was between 3 Five mana cost range units , I can only put one so this unit will no attack , so I just chose the one with higher hp to win on sudden death but my opponent refuse to play and I win anyway, there are some 2 epics in Untamed but don't have it and they are pretty expensive even for rent.
Problem comes mainly from only range units rule-set, Easy Solution: Forbid this mode together with ''Odd one out'' ''Even Stevens'' and no neutrals atleast in modern format to avoid not having any team to submit.
This has me wonder why there isn't a 3 mana cost ranged Life CARD in Chaos Legion and Riftwatchers where the the Life summoner is for ranged monsters, there isn't a 2 mana cost either there is one in neutral though, there are low mana cost life ranged cards in previous editions, hope on next edition comes lots of small archers for life lets give some love to General Sloan. Also it will help for the only ranged rule-set.
Something quite unrelated: the only magic Rule Set, make some summoners extremely strong like Bortus with Djinn Oshannus L1 can beat even some level 6 summoners, this is very convenient for bots that use a Level 2 summoner of all summoners, while average actual players has 2 or 3 level up summoners and will use this summoners in all modes, not sure if this is a problem but think it was worth to mention it.