Multiple glyphs of warding can't ward the same thing...
The target of the glyph of warding is listed as object touched or up to 5 sq. ft./level, and the spell's description says
Multiple glyphs cannot be cast on the same area. However, if a cabinet has three different drawers, each can be separately warded.
This prevents chained glyphs exactly as you describe, and for good reason. For example, were multiple glyphs able to ward a lone tiny box, triggering them all simultaneously creates disastrous consequences for the approaching army—seriously, a tiny box will be picked by someone and opened (especially if it's a shiny box), and if there are hundreds of glyphs of warding on that tiny box then boom—goodbye, army. (To actually run such a trick, try the spell explosive runes instead.)
...And a touch spell stored in a glyph of warding will affect the creature that triggers the glyph
The spell's description says
You can store any harmful spell of 3rd level or lower that you know. All level-dependent features of the spell are based on your caster level at the time of casting the glyph. If the spell has a target, it targets the intruder.
Emphasis mine. The spell touch of idiocy has as its target living creature touched, so a living creature triggering a glyph storing touch of idiocy will be the target of the spell despite the spell's typical casting method. (By the way, multiple penalties from multiple touches of idiocy—as they're from the same source—shouldn't stack, but ask the DM; a penalty is a little more complicated than a bonus, despite the lengths of those linked entries.)
Although the text isn't specific, it's safe to assume that summoned creatures from a spell glyph aren't random creatures from the summon monster list and instead chosen by the glyph's creator when the glyph is created. Likewise, a suggestion spell held in glyph should offer a suggestion that the caster chooses upon creating the glyph rather than offering a suggestion of the caster's choosing when the glyph is activated.
That said, this is a really expensive way to secure a wagon
A heavy wagon only costs 100 gp. Spending hundreds of gp to protect it is an unusual use of resources. If available, consider hiring some locals to guard it. They'll be thankful for the generous 1 gp per day that you pay them to guard your wagon.
In 5e, spells which deal damage require an Attack roll or a Saving throw. Without one of those, this spell would be OP at 5th level. Since this spell requires an attack roll, the damage that you can deal by teleporting an enemy 200 ft into the air seems balanced to me. Compare for example with the 10d6+40 damage for Disintegration (level 6) or the 8d8 damage to multiple creatures (cone) for Cone of Cold (level 5).
Best Answer
Teleport cannot be placed in a Glyph of Warding
In the spell description for Glyph of Warding, the paragraph regarding placing spells inside the Glyph says this, emphasis mine:
The spell Teleport, as written, targets "you and up to eight willing additional creatures of your choice", meaning that it is not eligible to be placed in the Glyph.
Traps laid by the DM can do whatever you require them to do
If you're a DM, you should be made aware that while a player creating a Glyph with this effect is prohibited, as DM, you're not required to strictly adhere to the rules set by any individual spell. Call it "Sigil of Arcana", a custom spell that doesn't have this specific limitation, and set it down in a room of the dungeon you're building. Or just make a Teleportation Trap that can be disarmed with Dispel Magic at a DC of 17 (or being cast as a 7th level spell), and forget making it a specific spell at all. You can create the effect you're going for without needing to reconfigure two spells that as-written won't quite do what you need them to do.
As a Player, you need a different spell
Teleportation Circle
Teleportation Circle is an obvious candidate, since it only requires a circle drawn onto the ground, and a Permanent Circle set up somewhere else. It has a smaller radius than Teleport though, meaning you'll be able to target fewer creatures with it. There's also considerable debate over whether Teleportation Circle strictly obeys the constraints for Glyph of Warding or not.
Misty Step
You might be able to get clever by using lots of Glyph of Warding's in the same place. Place a window (no glass or other obstructions) that has visibility of an area outside the tower no more than 30 feet away. Cast Glyph of Warding with your chosen trigger condition, casting Misty Step as the spell to activate, targeting that point with the Misty Step spell each time you do so. Then write conditions for these glyphs:
This method has a few obvious loopholes:
But it should work provided you create enough glyphs to handle an entire enemy party.
Dimension Door/Thunder Step
Same as above, except you need to resolve the debate over whether these spells' abilities to "bring an extra willing creature" interferes with the spell's ability to be put in a Glyph of Warding. I would generally rule it doesn't, but the DM may not feel the same way. If they do rule in your favor, Thunder Step increases the range to 90 feet, Dimension Door increases the range to 500 feet and eliminates the need for line-of-sight.