Everything is this section is subject to change.
This is where we get to unknown territory. There's a lot of variability that comes with porting a real-time DS action game into a turn-based GBA game, so please leave feedback as to what gives the most fun experience.
Battle System
Moves and Types
The current plan is to make the battles more interesting/reminiscent of Spec1 by giving every Spectrobe (and Krawl) species completely unique moves. These "signature moves" will allow every Spectrobe to be useful. A number of basic moves will also be shared between species. The only things the player will currently have to pay attention to with moves is Effect, Power, Accuracy, PP, Targets, and Type, with few moves giving stat boosts and even fewer giving status effects until later in the game. This is to remove some "pokemon-ness" from the system. That doesn't mean that every Spectrobe will be stuck as generic damage-dealers, but does mean that other fight styles will be a little rarer than in Pokemon, and limited by species, hopefully ending up keeping a similar mix to that of Spec1.
The types, Corona, Aurora, and Flash, will be unchanged from Spec1.
STAB has been removed as it has no place in a game where monsters learn moves of one of two types.
Additionally, the physical/special split has been implemented to give more range as well.
I believe these changes will keep to the spirit of the original Spectrobes but still work in a turn-based strategy environment. That being said, I am completely open to changing these things entirely if it is unfun or too easy, or anything really. So please leave feedback!
Synergy
Included as a nod to the "Beyond the Portals" mechanic where
certain Spectrobe species have a unique combination attack and as a replacement to Pokemon abilities. This mechanic will be expanded upon in comparison to BtP, with many more species combinations planned to be included in future. Simply, compatible Synergy Combos receive a 50% offensive boost in double battles.
Vilamasta + Bartolor --> Armored Bulk
Komanoto + Shimanoto --> Guardian Dogs
Naguryu + Grilden --> Draconic (Grilden not obtainable in this version)
Field 
A few things to note outside of battle:
You always need a minimum of 2 Adult Spectrobes in your Prizmod, as opposed to 1 Pokemon. This is a nod to Spec1, and is also because double battles will become the most common form of battle as the game progresses. Still, you won't white out unless all your Spectrobes are defeated (but you may be prevented from progressing).
Fossil locations and Vortexes will respawn when you leave an area and return. Minerals and Cubes will not respawn like this (but old Mineral locations may respawn as you progress through the story).
Child Spectrobes can't be sent out in battle. The game will ignore any Child forms in your party. You can't use them as fodder to heal your Adults and you can't switch-train them until you evolve them. But there's still a reason to bring some Child forms with you:
The purpose of having Child forms right now is to hunt for
Rare Deposits. These are found in precarious locations, and Child Spectrobes with unique attributes (such as being able to fly, having a hard outer shell, etc) will be needed to get the goodies inside. They will contain a lot of minerals, but also a Secret Spectrobe fossil - a fossil of a Spectrobe from
Beyond the Portals, not Spec1 - that can't be found anywhere else, so any collector should look out for them.