Without it, the swarm is lot less effective. Fungus can produce some sapro but they are pretty slow and the treefolks... well... One of them give the indestructible to forests, that isn't as interesting if the sappro aren't forests.
Your commander are interesting but I don't see how to use the red of your second commander here.
Well, at least at my group they would laugh if i would play
Life and Limb and then play an mass destruction. if you think its safer at your group, give it a try. Just dont focus to much on that card, since it could be difficult to tutor for a Enchantment in green.
About
Tana, the Bloodsower, i agree with you, you dont need to invest heavy into red, but she got trample, would be difficult to block in combination with Sidar and generates lots of saprolings.
Hmm.. On the second Thought, i got some ideas:
Impact Tremors,
Purphoros, God of the Forge. Ping some damage with every saproling you produce.