Things it should have: Stuff that explodes unless someone pays. Stuff that affects everything unless you pay more. Stuff that does other things if countered.
And newly: Trigger on things changing controller. Trigger on things changing colour. (Obviously, lots of stuff to cause those two)
I also rather like: 1: You control Target permanent that you control. Although it doesn't work as a counter to someone taking something from you, only makes a theft permanent. So I need to work on that. Perhaps: 1: Until end of turn, no one else controls target permanent that you control.
Modifiers as a cycle. Things like: "Flash - you may cast the next spell this turn as an instant"
Some of those seem low powered, they might work best with storage counters of some kind as a continual threat.
Phylactery - Black Artifact - As an additional cost to play ~this~ pay X life. ~this~ comes into play with X counters on it. If you would lose the game you may sacrifice ~this~, if you do instead of losing the game you have life equal to the number of counters on ~this~.
Hybrid tap/untap symbol.
Chimeric Mass deck. Colourless GU splash. Chimerc Mass Trinket Mage Energy Chamber Dragon Engine That jumping wall
Urza's mine Urza's power plant Urza's tower Some islands and forests
Some land search
Hopefully, it IS big and it IS clever. It's also insanely vulnerable to removal, so probably would want some unsummons and some way to get artifacts back from the graveyard.