I am not entirely Clear on what your question is. I imagine you are asking whether an organism can develop or evolve in such a way that it has the internal systems of a Plant (regeneration and such) as well as the higher functions of animals (locomotion, thought). i.e. something like Dc’s Swamp thing.
This is most likely going to turn into a Biology lecture. And I will be making some conjecture where my expertise is lacking. But, here are my thoughts.
An Organism Capable of locomotion and some manner of self-awareness, does so at sacrifice of other traits, including a modular cell nature. As far as I am aware. Let me Explain.
In RPG terms, i think the biggest challenge for such an organism would be the trade off between High Physical Stats and Processing power. The modular structure of the plants enables them to grow to sizes unattainable by most animals. It facilitates damage reduction and high regeneration such that they can recover being cut down provided the right conditions are met. But this comes at a cost of lack of cognition.
Any animal no matter how small, has a sense of self. They are aware of their own body and have at least the most rudimentary instincts. Even a cockroach or an earth worm has self-preservation instinct. While there are some plants with similar defensive characters, they are more trigger based than instincts. (E.g. Tactile/Odor based irritants & allergens)
The plant body has no centralized structure. Which means any plant cell taken from the whole can perform all the functions of the whole. And this range of functions while impressive are limited in the scope of terms. In Biochemical terms, a cell can perform only so many reactions at a time. Or an interval. If it needs to do more, add more, it must sacrifice some other to make space. It needs more Processing power.
Take this scaled up Macro analogy. Whales were once terrestrial mammals. In time they evolved to be aquatic organisms. And concurrently their physiology adapted to suit their new evolutionary path. Their forelimbs flattened and became flaps, the hind limbs relatively unnecessary for swimming, regressed completely and is now just a vestigial bone making their bodies more streamlined. And the freed up energy, previously spent to development of limbs was re purposed for better respiratory capabilities and lungs that can withstand the strong pressures in the deep waters.
Similarly, in the procession leading from Cell based life forms to Kingdom Animalia, the cells instead of doing everything by itself started to delegate and compartmentalize tasks. In Multi cellular organisms Cells began to Differentiate to accommodate specialized tasks. These specialized cells could do only a fraction of what the originals could. But now instead of a single cell performing n number of tasks, there were x types of cells each performing n/x number of different processes. (An oversimplification. Differentiation in actual physiological systems rarely follow set division of labor)
The remainder of the cell’s available biochemical potential, i.e. its Processing Power could be allotted to new tasks. And believe me you, the capability of self-propelled motion is a game changer. Now, the energy sources available to you are as large as the expanse you can cover on your own. This albeit means that you’ve sacrificed the capability to utilize some of the micro nutrients and minerals.
With Locomotion comes more specialization. Because remember, now you are actively interacting with your environment as opposed to be molded by it. And each specialization develops it own sub-specialization.
All this necessitates the need for a centralized control scheme. Because the old way of moving by ‘sensing’ the higher concentration of nutrients is not always viable over the now (relatively) large distances. Which necessitates more processing power, which needs more energy and more specialization. And so, we ascend further in the ladder of complexity.
And Specialization is the death of Flexibility. In the current scheme of complex organisms all cells in the body have, in theory, the capability to perform all necessary physiological functions. But not at the same time. These progenitors, (Stem cells) become differentiated to serve their assigned role as early as day 5 of development. (Note that we’ve shifted from talking about Asexual cloning methods, to gene mixing in form of sexual fertilization). From then on, until the death of that organism individual groups of cells performs only the function assigned to them.
And as mentioned before, this system is so welded in place that such groups of cells are virtually irreplaceable. Except the Brain. Which is ‘literally’ Irreplaceable. The Brain, one of the crown Jewels of the Animal Kingdom, and the greatest energy sink in the body (20 percent of total available) is so vital, stopping its function for more than a couple minutes would end that organism’s existence. Even when all other organs are working perfectly. And it’s so individualistic replacing it with a spare is, let’s say is NOT the preferred fix. The condition called Brain death results in a body which in theory is in working condition; and hence one of the reasons that victims of brain death are treasure troves for multiple organ replacements.
To Summarize: The very reason that you are ‘aware’ of your existence means you’ve given up the chance for the unbelievably broken ability to regenerate from the smallest of parts.
While the lack of ‘awareness’ plants and other cellular entities capable of such feats are not in a position to, let’s say ‘appreciate’ it.
Back to the game analogy. You are a mage that sacrificed physical vitality to gain intelligence for casting spells. While the other side is a passive Berserker/Tank that gained near infinite regenerative capabilities but are nothing more than collected mass. (Implying plants are dumb, is an incorrect and highly inaccurate statement. And in some circles, intelligence is not measured in same standards to plants as they are to animals. But you get the idea.)
P.S. I’m aware that some parts of my answer have run far, far off tracks. But if I was able to assist it in any ways I’ll feel satisfied. As was this a good thought piece for me.