Like most Pokmon cards, the value of Latias depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Delta Species)
Keep in mind that Black & White was when Trainer cards began being called Item cards, so if you utilize Junk Arm, you can grab Trainer cards from HeartGold & SoulSilver (Rare Candy, Pokmon Communication, Pokmon Reversal) or Items from Black & White
The PSA 9 versions of the card sell for an average of $100-300, making this a valuable card but not a huge deal
While the mechanic does appear to be enjoyed by fans, Wizards of the Coast doesnt often print Meld cards
When Unwilling Vessel dies, create an X/X blue Spirit creature token with flying, where X is the number of counters on Unwilling Vessel
That said, I think it will be an all-star in decks that can abuse the token production