Riot games sacrificed the best game mode for a theme, "one for all" would be no problem tho.
I understand that this is "Snow Battle ARURF" and not "ARURF" where it's themed on winter, snow ....
they could simply unlock the winter skins, put Santa's hats on skins not included in the theme or some thing similar
it would be much better then limiting the champ pool to 60 they seriously mismanaged .
its supposed to be fun now you'll only see the same 10 boring champions for 2 weeks even with the "All Random" which was made for this reason.
+ its not gonna be an OP vs OP game like it used be, but a one sided game the team with an op champion like shaco or jax or... will certainly dominate the game cause there is not enough champs from this "Pool" to possibly handle them.
and that's it wait for ff and try again you might get an OP champ and dominate the next game when the enemy team already gave up, where is the "Fun" ?.
PS:nothing is gonna change in PBE same goes for other live servers next patch,so lose hope already and accept it
Good Luck .