imma be leaving my ideas in the replies of this comment

metronome active that gives random effect (30 seg recharge time)

toxic venom item that works like frosty mint, but instead of freezing, it poisons enemies on contact (quality 1)

greed mode where enemies drops far more coins, after each level there's a store, its normal floor themed, BUT the only way to get babys its through the store, there's only two babies in sale, and depending on the heart cost it will cost more or less coins (example : farting baby costing 33 coins and hallowed ground costing 333 coins, i also imagine having a extra zone for the babies like with the charger tokens)

succubus baby that works like hallowed ground, but it only buffs damage, deals constant miniscule damage in a 3x3 area, and it costs 225+ hearts (the price increases 85 hearts by each one alive in the map)

Host Hat active item that gives explotion inmunity to a baby (66 second recharge), it would be unlocked by making explote 20 mulibooms before it gets to the 7th layer (via putting babys in front of them or something)

pupula duplex baby that has tears 3 rails wide, it pierces through all obstacules and enemies in the side-rails, but not the enemies in the front, it does brother bobby and has fire baby recharge and it costs 200 hearts (200 because its kinda like little steven and ghost baby, but a little but better)

"marked" baby that works kinda like mortar monkey from the bloonds td series.

 when placed, it makes appear a "mark" and it trows elevated tears towards that "mark" constantly, regardless if there's a enemy on top of it, it does lil loki's damage and it has sinergies with some babies, if placed in front of it, like mongo baby (a few examples could be:

Fire Baby: it throws misiles [like dr. fetus] at a far slower rate, with heavy damage and an increased 5x5 area, but it get's weaker the further away from the impact zone, heavy damage at the 1x1, normal damage in the 3x3 area, and light damage at the 5x5 area.

Ice Baby: it dosen't increases range, does normal damage in its entirety, but at the 1x1 area it completly freezes enemies and at the 3x3 zone just slows them now, but it has a slightly higher fire rate

Spider Baby: places a short timed 5x5 spider web, and when it hits an enemy, it does the  parasitoid efect [spawns 2 friendly flies], it has a normal fire rate)

It costs 300+ hearts, +200 hearts cost per sinergized baby, +75 hearts per baby alive

incubus baby would be the imitator from pvz 1, 35 sec recharge minimum, if baby's recharge time its higher that that, it would adjust acordingly

Active item "The book of belial": reusable power pill, 120 sec recharge

the mulligan, brother bobby but has a 1/6 chance for The Parasitoid effect, 125 heart cost and brother bobby recharge time

dingle berry baby, "mystery egg" baby but with firendly dips, costs 125 hearts and 15 sec recharge

Lil brimstone: deals 4 damage per tick, 9 ticks per charge (36 dmg per charge), pierces through obstacles and enemies, 2,32s attack speed, 20seg recharge time, 200 heart costs.

this was an obvious one

i started  to use the wiki to describe these in a more acurate way

Lil abaddon: Lil abaddon shoots a black brimstone attack around him, remanesant to Baby Pluto, it can reach enemies in a 3x3 area, it does 7 damage per tick, 9 ticks per charge, 2.55s speed, 100 HP, 15s recharge and 250 heart cost

The Twins baby, this baby would both generate hearts AND attack, the baby attacks almost identacly to Brother Bobby, while passively producing hearts half as powerful as Little C.H.A.D.'s hearts, only giving 25 hearts per production, it has 100HP, 17 damage per tear, 1,16s attack speed, 30s-40s heart production speed, 10s recharge time, unlocked by beating a level without using monster manuel, heart-producing babies or attack babies (unlocked by only using one of the babies in the next list: Cube of Meat, Bob's Brain, Hallowed Ground, Big Beautiful Fly, Farting Baby, Multidimentional Baby, Spike Baby, Tooth & Nail [exeption], Acid Baby, Dry Baby, Pashcal Candle, Snowball, Lost Soul, Juicy Sack, and finally, Ball of Bandages)

That's really interesting.

I'd say it's an intentional typo.