Acidic ones sound safe.
Cryo ones would require properly implementing the cryo damage - messages, armors and monster resistances.
Heat blobs would require some protection for other blobs - currently slime pits are all flammable. They'd need some mechanic to separate them from acid blobs so that they wouldn't just be acid blobs of different type.
Dodgy blobs kinda go against the whole blobby nature. High hp ones (with regen?) would be safer.
Slowing down sounds good.
Splitters wouldn't be easy to implement (they'd need to know when to split and when to merge), but would work too.
Acid blobs should dump acid when they die/split, but probably not any other time - doesn't fit their general behaviour.
Heat/Cryo - meh.
Dodgy - I completely agree it being the wrong flavor... blobs that slowly regen would be good, but you'd have to be very careful with any spawning mechanics (though those are all out, at least for now), of things get really crazy
The amoebas already have a slowing attack, and the slime pits also slow you.
Blobs already split - it's the merging that would need to be managed, and a base mechanic for that is actually quite simple: the "merging" type blob would merge with any other blob whose square it wants to move in to. The resulting blob would get all the HP of both and be the same size as the larger of the two blobs, or one size larger if they were the same size. The type of blob would be whichever blob was larger, or 50/50 for either type if they were the same size. That only leaves handling max-size blobs.