This mechanic already exists. It's called buying a unit and keeping it in your hand. Particularly effective with token minions, Sellemental, Sun Bacon Relaxer etc
Spending 3 gold on trash minion just to get back 1 gold back in the future (but only if you have room on the board) is far from the proper gold banking system and it's not very helpful when you are already behind.
I have said that many times already, this mode needs some come back / anti bad luck mechanic, because without it, there's simply too wide gap between high and low roll. If you get bad pools from Bob during some key turns (like 7-10), you're screwed and most of the time there's no way to compensate that later on (unless you get many really crazy rolls). I think banking your gold for the next turn would be nice, because it would allow lowrollres to come back and not waste gold on trash minions or re-rolls, just because you have to spend it anyway. Maybe not all your gold, maybe not any time you want (to balance things out), but some form of banking would help a lot to fight back against RNG.
There's something bad about a meta that if you get even a little bit unlucky it's over. I understand a bit why they feel the need to make every hero and class more and more powerful, but they are skating a bad line.
It kind of reminds me of arena, it was great before when you could draft badly but still make the most out of a bad situation, that is long past as the bucket system ensures everyone has a constructed level deck.
Not quite the same situation, but I doubt we'll see battlegrounds go the opposite way, it will probably get progressively worse. There's a lot of lines that are pointless to go down because they get out scaled early.
True, it often feels like the game is decided very early, purely by RNG. If you don't have any power house by turn 7, while other players do, you're done, because they will grow from now on (every single turn), and you will fall behind more and more.