Hello, fine peoples!
As I am making a character that uses this for an RP, I thought it'd be good for me to post this thread showing a few of his cards and explaining the gimmick.
Really, the "gimmick" is simple and has actually been explored before, sorta. Battle Pack 3: Monster League was a pack that Konami released to support draft/sealed pack play. In it, Konami made a "Special Rule" that made all monsters all types. This allowed the format to work with a bunch of various monsters while also allowing them to print type-specific support cards (such as "The Warrior Returning Alive") without worrying that a player wouldn't be able to use it.
Basically, that is what the hybrid-type is: a monster that is all types at once.
Under normal conditions, this would be overly powerful, so (for the most part) cards of this type are usually Normal monsters or are pretty bad. Examples below:
One-dimensional object that subsists using energy from our world. It is unknown whether it is truly alive or not.
A dog that has an unusual aura about it. It seems to be loyal to a being that cannot be seen.
You can target 1 monster you control and 1 card your opponent controls; destroy this card and those targets.
A creature of immense power that is able to open holes in space-time with its howl. Its stomach seems to be a wormhole as it never seems to get full.
Lash, Lord of Entropy
If this card is added to your hand this turn, this card can be Normal Summoned without Tribute.
...yeah, generally pretty bad. This design needs to be carefully balanced, just because there is SO much type support that could end up making any "ok" hybrid monster broken.