Mimicry might be the sincerest form of flattery, but originality is alot more fun, isnt it?
Anyway... here's how to do what you want to do.
(1) Bomb Flowers
These are do-able, certainly, but they won't interface with bomb secrets built into Zquest. What you'd want to do is have an FFC you can pick up (someone already did a script for this) and then, when you put it down, it becomes a lit bomb. Problem is, we currently have no scripting control over weapon sprites (like swords, arrows, etc). Now, you can SIMULATE this by making a series of FFCs that animate and damage enemies just like a bomb. But it won't trigger bomb secrets. For that, you'd need to make ANOTHER script that detects the presence of the simulated bomb, and changes screen combos / plays secret noises accordingly.
So, impossible? No. Conceptually hard? Not really. Burdensome? Absolutely.
(2) Breakable Swords
This one's really easy. Have an item script that increments a global variable every time the item is used (or every time it strikes something; that is, when the player is close to a wall or enemy). When the global variable is high enough, the item is removed from the player's inventory.
(3) Blue Fire, etc.
A custom item that makes a little graphic is really easy. Just like with bomb flowers, though, you can't interact directly with secrets. So you'd need a second script (ice wall?) that checks to see if a blue flame ffc is close to it, and if so, reacts just like secrets were triggered. Much easier than the bomb flower.
(4) Deku Sticks & Fire
Item script activates a variable or sets an FFC in place; then a carryover FFC script draws a stick out in front of Link as long as the button is held down. That part isn't bad. Maybe start with a slashing animation and simulate a sword attack? Not to bad. As for lighting on fire, you could check to see what combo number the stick is on top of, and change the graphics when it's above a flame. Thats not bad either. BUT just like above, your burning stick will not be able to directly interact with burn combos. You need a custom script that activates when the burning stick is placed over it.
(5) Checking for Items
This one is, like, two lines of code. Please refer to the Documentation thread over in the scripting forum.
(6) Epona
This has a few elements:
(1) A dummy item that uses Link Tile Offset to make him look like he's riding a horse:
(2) Several FFCs that make up the body of Epona and follow under Link. Perhaps they damage and push away enemies that get to close. Also should speed up Link's movement significantly. Wouldn't be too hard to make them hop over one-tile-long unwalkables, either. The hardest part here is drawing all the animation frames for the horse.
(3) An item script that gets you on the horse, and other sundry scripts that make you get off of it. Maybe use a special flag to make no-horse-here tiles.
Difficult, but interesting and totally doable.