Is it possible right now a mod with alretnate upgrades?

Is it possible already? Without any/major code modifications?

Just asking…

What do you mean?

There is possibility of alternative units in one level.
For example. for building 30, 37 you assign Troglodyte/Infernal Troglodite, for building 44/51 you assign Golblin/Hobgoblin.
Now it works only if building 30 builded first (if 44 builded first, growth sets to 0).
They share common growth (of Troglodyte).

Partially. It is possible to give multiple upgrades to creature but upgrade UI can fit only one item. So creature will aways upgrade to first available upgrade.
Workaround it to allow upgrades to “upgrade” into each other. Far from what can be called as intuitive.

Second problem is that in towns buildings can give only one creature. Workarounds:
a) call it feature - to receive alt upgrade player must built appropriate structure.
b) add “mode” : “auto” to building with second upgrade. In this case it will be built automatically.

Try this to see how it works

"baseCreature" :
  "upgrades" :  "upgradeA", "upgradeB" ]

  "upgrades" :  "upgradeB" ]

  "upgrades" :  "upgradeA" ]

This is closest you can get to alternative upgrades.

Polish modders are working on 3rd upgrades mod for VCMI:

Hope they will finish it one day. Seems work is going well.
These DEFs for dwellings maybe also used for alternative upgrades later
( … 74&page=22)

Seems like Kuririn already shared his VCMI mod on new upgrades: … e=32#76478

It’s only in polish now.
And it’s unstable. And not all dwellings are redrawn. But for those who want to study VCMI it’s cool - it’s new staff.

New version Nowe ulepszenie (New Upgrade) available in VCMI mod list