I'd happily let my players draw mustaches or phallic objects on a sleeping character's face, but if the topic of involuntary sex came up, I'd warn them OOC that that sort of behavior isn't tolerated at my table, and will result in me ending either their character or the session, depending on the situation. If needed, I'd state that the character is immune to penetration of any kind as an extension of the "immune to harm" clause, but honestly I trust my players not to even go there. We're all adults, even if we sometimes don't act like it.
As for prolonging sleep, there's a certain point at which people stop sleeping and are simply conscious but resting instead, which I'd call at typically 8 hours per the normal resting rules for most games. I personally welcome creative uses of the item, but if you try to pair it with a sleeping spell, the target becomes immune to the spell per the item's effect, which means it would fail to work. Tossing unconscious players into monster pits as bait is fine with me though, especially when the beasts decide to drag the meat popsicle back into their den for later.
Anyhow, let's get some new items created!
This slim-fitting garment is sewn from the hide of a large feline. Nine tiger eye gemstones adorn the vest's collar when created, and a clasp in the shape of a silver claw holds the vest shut. The vest grants the wearer confidence that there's more than one way to arrive at a solution. Once per day, the wearer may reroll an attack roll, skill check, or saving throw as an immediate action; if so, the second result must be taken, even if it’s lower. Should the wearer be slain, the vest heals the wearer for 5d8+9 points of damage as an immediate action as per the breath of life spell and one of the nine gemstones turns black. For each black gemstone the vest bears, the wearer gains a cumulative -1 luck penalty on attack rolls, skill checks, and saving throws.