After the comment of ionanis where he mentioned

IOANNIS said: Gold Caduceus cost is 5000 and Silver Caduceus cost 2500, exchange 2 silver for one Gold. 

i began to think why they could not upgrade like the elixirs .... and then i thought that option the upgrading would be a great solution for all the unused grade 1 and 2 skills stones that we get free in game.... so my suggestion would be

could it be posible to upgrade skill stones like you do with the elixirs in the sanctum asclepios (i never get right the name lol)?

we all are getting lots of 1 and 2 that most of us we dont use, and we could recycle upgrading them into higher levels the same we do elixirs or the same we level up guardians, so they will become of use for all players, regardless their level....

Would this be possible?