This suggestion is fairly dependent on a spellbook system similar to that suggested by Winnihym in this thread https://forums.elementalgame.com/386267 but in combination i feel they would allow for great customization and flexibility.

So how about separating shards and elements in such a way that when a shard is discovered a channeler must stand on it and cast a specific spell that could be unlocked by early research into shards allowing it to be "tuned" to a specific element, before this shards are blank slates. This choice may also be expanded into allowing the shard to channel raw magic granting a substantial amount of essence/mana, perhaps +5 to base along with the current percentage.

In this process an improvement is built on the tile connecting the channelers magic essence to the shard allowing spells of the chosen element to be cast and granting a powerup consisting of a decent amount of experience giving an out of combat method of leveling.

This improvement can only be destroyed by a rival channeler casting the same spell on it, the cast should take a few turns giving the chance to stop the process but if it completes successfully the enemy channeler may now take control of the shard and tune it to a different element, some penalty backlash might be added giving the original channeler an ability penalty for a few turns or some damage to make things more interesting and in the case of the shard being tuned to raw magic the original channeler should lose the base essence/mana bonus granted by it.

Of course there's a chance of this making things too easy, not giving the challenge of hunting down that elusive fire shard to allow you to burn down your opponents lawn but this can be avoided by giving the map creation option of "Neutral Shards Yes/No"