Because a demoman is not a demoman without them.

MAGNET SPARK LINE
(2* Magnet Spark -> 3* Magnet Bolt -> 4* Magnet Overload -> 5* Electromagnetic Tempest)
(2* Magnet Spark -> 3* Split Spark -> 4* Tri-Spark -> 5* Thundering Quartet)

The Magnet Spark is a different kind of bomb. Its initial blast is tiny and weak. However, it releases a space-wide electric spark that will remain for two and a half seconds plus another half second per upgrade, dealing damage to targets it touches, and mimicking the motion its user makes after the explosion- but from the point it started! In other words, if you lay the bomb by a low wall and run away two spaces, then run back up two spaces after it explodes, the spark will be two spaces from the point of explosion. This can be useful for attacking a turret or hitting a distant target. The damage is Dark-Ret-style scratch-damage-over-time, but becomes powerful in tandem with its Fair chance of Moderate Shock.

The Magnet Tempest line, along with the Magnet Spark itself, deals normal damage and Shocks enemies. The Split Spark is where it gets odd. Split Spark releases two Elemental damage sparks that are half a space wide, each with less damage (and no more Shock) and only a quarter second extra per upgrade (as opposed to a half second), but there's two of them! The sparks shoot out perpendicular to a hypothetical line drawn from the bomb to the player, going about two spaces before going into attack mode. Tri-Spark shoots out three sparks and Thundering Quartet shoots out four; the third and fourth go away from and towards the player, respectively.

How good would it be at distance hitting? The fuse would be long enough that someone in full Mercurial could get ten spaces away.

The sparks could not travel or hit through static objects (like walls) or mist gates. While I realize it would be great for killing spawn campers in Lockdown, I don't want things like Charred Court to become a cakewalk.

CHAIN BLAST BOMB LINE
(2* Blast Bomb -> 3* Chain Blast Bomb -> 4* Expert Chain Blast Bomb -> 5* Chain Reaction)

Upgrading from the Blast Bomb, the Chain Blast Bomb has a bit of a longer fuse, but utilizes a special feature. Laying another bomb on top of the first Chain Blast Bomb will stick the second bomb to the side of the first, leaning toward the direction you were facing when it was planted, and reset the bomb fuse; this particular feature is much like Zeddy's Stack Bomb. Upon detonation, the first explosion, which is about the size of a Blast Bomb one stage lower and slightly lower damage than the same-stage Blast Bomb, launches any second bomb up and causes it to land about four spaces in the direction it was leaning. Said bomb explodes a half second after contact with the ground, making an equivalent explosion.

The 4* Expert Chain Blast Bomb can have two additional bombs stacked, and the 5* Chain Reaction can have three; each one launches in the direction the bomber faced, allowing for a chain reaction that sends the bomb around a corner. Chain Reaction gives the bomber considerable range, allowing him to use his bomb like artillery. Should the bomb go over a low wall, it'll airburst immediately upon contact with the "ground" and keep the chain going. However, this technique takes considerable setup. Blocks will stop the bomb (somehow) so it can't hit switches that shouldn't be hit.

TELESTRIKE BOMB LINE
(2* Telestrike Bomb -> 3* Prime Telestrike Bomb -> 4* Supreme Telestrike Bomb -> 5* Blast Rift)

Another oddball, you can't hit a party button while this is primed to explode. Why? Because when it explodes, it doesn't explode; it pulls you through an interspatial rift into it and YOU cause a detonation. The blast created is based on the defense provided by your suit of armor; the type you block determines the type of energy that is shunted out of the time-space continuum and subsequently into the targets' faces. The numbers remain the same, but the damage changes based on the armor suit. So if you're wearing Silvermail, you'll blast the enemies caught in the way with split Shadow/Piercing damage, where if you're wearing Mad Bomber, you'll hit 'em with split Normal/Elemental instead.

The other aspects of the bomb are always the same. It deals heavy interruption and some knockback and has a slightly smaller radius than the Nitronome, while packing no status effect.

And now I'm ready for all the reasons that this is awesome/sucks/is balanced/is overpowered/will work/will never work/isn't bomblike enough/doesn't need to be bomblike enough. Go nuts, I need your criticism to refine this into something that'll work.