Kylo has a cracked crystal and uses the side vents to release excess energy to maintain stability of the saber. Snoke told him to make an old type of lightsaber, whatever that will mean in Disney canon.
Kit Fisto used two crystals with some design differences that allow under water function.
3 crystals were mentioned to be used in a saber Luke was given in Heir to the Jedi.
The Sith used alchemy to supposedly remove impurities and form a stronger synthetic crystal. Quinlan Vos believed Sith sabers to be inferior. Perhaps this is the 'imbalance' that led Jedi to use Ilum and natural crystals. The Sith may have ultimately settled on synthetic, because the Jedi attempted to control the mining of natural crystals to prevent Sith from having them. The Emperor outlawed lightsabers in an attempt to prevent Jedi from using them after order 66. The new Jedi order led Luke to try alternatives to lightsaber crystals. Anything that can focus the beam can be used with differing effect.
The typical saber electronics design most likely won't fit every crystal, and shards would make anything resulting unstable. The crystalline structure of a thing is based in chemistry. So, it's more than just melting, mixing and solidifying everything. Shards would result in multiple focal points, defeating the purpose. It's a focusing crystal. Perhaps Sith alchemy could combine shards, however, it would take years to improve the already used Sith methods of forming a crystal. I'm not sure using shards would even help. If you know how to form a multi-powerful crystal with full effects, then you may not even need shards. It's the skill of the alchemist that would determine the result.
In general, the Jedi allow the force to guide them to select from what nature has provided, while the Sith will attempt maximum control and power from their weapons. As to whether or not the Sith alchemy really does make a better crystal is uncertain. Different times in the stories have suggested it is and other times it's not more powerful. The Sith often use talismans etc. to increase their power, while Jedi use training.(ref. Book of Sith)
I think a difference in electronics design in combination with multiple crystals may be needed for what you're wanting. You're in line with Sith who want to be loaded with lots of talismans, alchemy and enchanted items. But they just don't all work together and often are harmful to the user. Crystals of different materials would have their weaknesses as well. If not, everyone would do it. We all want to load up with everything and be all powerful. I think just about everyone has had this idea before. It's always easier to think of adding powers than struggle to decide on just one. It probably started with games, but some stories pursue this vein of thinking. The stories usually make a consequence involved.
Not unlike...They make an RGBA. They make an RGBW. There are technical limitations and expenses to make a ROYGBIV LED.
