Your idea is great but there are ways to make your datapack much more efficient.
So first, as placing a spawner in survival doesn't keep its data, you can just store all of its data in a special tag in the dropped item. So just use :
{
  "source": "{}",
  "target": "SpawnerData",
  "op": "replace"
}in the loot_table. With this, all of the spawner data is stored in the dropped item tag SpawnData.
Then you want to detect when the player places a spawner. This can be easily achieved with a placed_block advancement.
In the reward function, store the SpawnerData tag of the held item in a storage and start a raycast function. Once you get to the spawner, simply do data modify block ~ ~ ~ {} merge from storage <> SpawnerDataAnd that's all !
Oh there is something else, you should make so only pickaxes can "harvest" spawners because for now, any item with silk touch can do it.
This can bring your datapack to only ~8 commands and 5 files.

Doesn't work man