As promised i added variable spawners to the plugin:
Creating:
To create a new variable spawner run the command "/es create variable <default spawner> <new name>"
Here the default spawner is the default values for our spawner. Once the command is executed some extra information will be asked via chat i.e:

• Change type:

This is what will cause the spawner to vary. Currently i have 3 options:

1. spawn = change everytime an entity spawns
2. placeholder = change with change in a numerical placeholder (PAPI Support needed)
3. time = change after a fixed amount of time

• Data Entries:

This is the data regarding a changing spawner. Given in the format:
"<min>,<max>,<spawner>".

1. Here the min is the minimum value of placeholders to have & max is the maximum value for placeholders to have.
2. If you have time or spawn set as change then max is the % chance for this spawner to be chosen

Note:
Currently spawner upgrades are not compatable with variable spawners.