Since is seems like everyone wants panda forms to be permanent... here would be my "rough draft" for how it could look.
Feel free to hate on me all you want
Panda Earth -
*When evolved has the same stats as unevolved panda did
*Tree walls removed, replaced with stone walls.
*Earth/Storm/Fire escape removed, replaced with Stone Shield... panda becomes invincible for 5 seconds (similar to radioactive)
* UPGRADE: Stone Skin - 8 tiers each adding 4 armor to the panda.
Each tier costs 250 lumber and 1 gold more than the last, starting with 250 lumber 1 gold.
*UPGRADE: Golem Walls - Same as currently.
*UPGRADE: Obsidian Golems - Unlocks an upgrade to golem walls, obsidian golems, making the golems max hp raised to 1250.
Upgrade Costs 3000 lumber 30 gold.
Walls costs 1000 lumber 10 gold each to upgrade
Requires: All Golem Wall Upgrades, Stone Aura
*UPGRADE: Stone Aura - Gives all towers/units in a 800 radius a +10 armor boost.
2000 lumber 15 gold
*ULTIMATE TOWER: Sentinel - Large golem tower which hurls boulders that deal 100 damage and have a 15% chance to stun the
titan for 2 seconds. When held as an item gives the holder a 15% chance to stun the titan for 2 seconds.
Panda Storm-
*When evolved has the same stats as unevolved panda did.
*Earth/Storm/Fire escape removed, replaced with storm surge. Increases movement speed by 250% for 5 seconds.
*Tree Walls removed, replaced with Storm Walls - same as most walls in the game.
*Storm spires are another basic tower panda can now build, they have only 800 range and do 35 damage.
With Advanced Storm Mastery upgrade, can be upgrades into....
-Static Storm Spire: Channels its lightning into static electricity, providing a +10% attack damage boost to towers in a range of 1000. Damage upped to 40. Costs 6g to upgrade
-Ranged Storm Spire: Upgrades range to that of panda storm's current towers.
3g
-Unstable Storm Spire: Has a 1% chance to do 20x damage.
4g
-Rapid Storm Spire: Increased attack speed from panda storm's current towers.
4g
-ULTIMATE TOWER: Storm Shrine - Deals 50 damage, very fast attack rate, and can attack up to 5 targets at once. When held as an item, the holder's attacks bounce to nearby targets, doing less damage with each bounce.
90g 2000 lumber.
*UPGRADE: Advanced Storm Mastery - Allows panda to upgrade his basic storm spires into other forms of storm spire
1000 lumber 5 gold.
Panda Fire -
*When Evovled, gains +300 hp and +5 armor, everything else stays the same.
*Earth/Storm/Fire removed, no new escape.
*Tree walls replaced with magma walls, same as most walls in the game.
*UPGRADE: Inner Flame - Panda ignites himself permanently, dealing 75 damage to all nearby targets.
10 gold 2000 lumber
*UPGRADE: Cone Of Fire - Attack that deals 300 damage to targets in a line, 60 second cooldown.
20 gold 2000 lumber
*UPGRADE: Fire Golems - Allows the panda to build fire golems, fire golems have the same stats as dranei's battle constructs. Each fire golem costs 1 gold 300 lumber to build and feeds 2 gold to the titan when killed.
20 gold 1500 lumber
*UPGRADE: Erupt - Allows the panda to erupt, gaining +1000 hp, +20 armor, +100 damage and increased attack speed for 20 seconds.
3 minute cooldown.
Requires: Inner Flame, Cone Of Fire, Fire Golems.
*ULTIMATE TOWER: Volcano - Same as panda's current fully upgraded volcano. Gives +30 attack damage when held as an item.
90 gold 2500 lumber
Misc. -
*Panda keeps all his normal builder buildings once he transforms
*Pandaren's box removed
*Vault of elements can only permanently evolve
*Remove battle panda upgrades
*Vault of elements costs 60 gold, since permanently being able to adapt to what is needed in a specific game is a bit overpowered for 20 gold (imo).
*Evolving a panda is free once you get a vault of the elements.