The only thing that prevents Brudiclad from being overpowered is that when going through the token copying phase, you are only copying the base token values, so if you're trying to copy a token that has a base power and toughness of 2/1 but has multiple +1/+1 counters on it, these won't transfer over to the copies, and the copies will still be 2/1.
The one Sol Ring swung games a lot more than one Mox would have in its place
Five toughness is massive, so unless opponents pack Swords to Plowshares, Vindicate, and/or sweepers, they might be in for a bad time in the late game
This allows you to bank spells for later, spread the mana cost over multiple turns , and, most importantly for Spider-Man 2099, cast those spells from exile