I need a rules lawyer to help me out on this one before I present in to my DM. I've pitched him the idea and I've done my research on Symbol spells. For the ease of everything I'll use Symbol of Death as the example spell even though it's not my intended use since most of the other Symbol series spells refer to it mechanically.
It makes a note:
"You can't use a symbol of death offensively; for instance, a touch-triggered symbol of death remains untriggered if an item bearing the symbol of death is used to touch a creature. Likewise, a symbol of death cannot be placed on a weapon and set to activate when the weapon strikes a foe."
"You also can attune any number of creatures to the symbol of death, but doing this can extend the casting time. Attuning one or two creatures takes negligible time, and attuning a small group (as many as 10 creatures) extends the casting time to 1 hour. Attuning a large group (as many as 25 creatures) takes 24 hours. Attuning larger groups takes an additional 24 hours per 25 creatures. Any creature attuned to a symbol of death cannot trigger it and is immune to its effects, even if within its radius when it is triggered. You are automatically considered attuned to your own symbols of death, and thus always ignore the effects and cannot inadvertently trigger them."
Finally: "A symbol of death can be removed by a successful dispel magic targeted solely on the rune. An erase spell has no effect on a symbol of death. Destruction of the surface where a symbol of death is inscribed destroys the symbol but also triggers it."
All of that said it appears legal to apply the spell to movable object since the trigger area is all that's important. I should also be able to attune the party (except Gary, f*&@ Gary) to the Symbols during rest time.
Does this mean I could throw it on a covered shield and just take off it's cover in combat? As it's caster I'm immune to it's effects.
Would this work on something like a brittle clay plate? Could I use said plate like a discus on a square to 'break' the symbol and trigger it? If that converts it into a 'ranged attack' would dropping it at my feet/smashing it work?
You're going to get some pushback. The first quote you've cited states that you cannot use it offensively. Essentially forcing your foes to view it is pretty offensive.
Frankly, the spell is a bit self-contradictory and could use some clarification.
I'm okay with pushback, I want it picked apart so that I have a solid argument for/against to hash out with my DM so he can make the informed decision to allow my use of it or veto.
My interpretation for it's use specifies what sort of offensive action it entailed as being prohibited. I've seen (and played through) dungeons where it's used as more than just the visual/touch/proximity landmine.