A little dessicant is all you need.
I am not sure what you mean by this but a little dessicant is not going to do very much. Silica (Dessicant) absorbs moisture until it's full and then does not absorb more until it's heated to allow the moisture to evaporate.
At one time I thought that dessicant was the holy grail of moisture control when in fact it's not. It is a good way to dry out latent moisture in packaging but only when the package is sealed. The size of the dessicant package has to be in proportion to the amount of moisture it should soak up from the environment.
Putting exposed dessicant packs in a car won't keep the car dry, nor will dessicant packs keep the inside of a case dry.
On top of that a reduction in moisture is not necessarily something that will prevent a cue from warping. What does that is the way it's made first and keeping it in a stable environment second.
We had a box of "Cobra" cues in our warehouse. These were Taiwanese made cues, four pointers with veneers. They had been made around 1990. They had sat in the warehouse of a well known distributor for a decade and then they came to us and sat there for another six years before I stumbled on them.
I went through the box and picked out the ones that were straight and sold them as blanks for both the butt and the shaft. Out of 50 cues probably 20 or so were dead straight and the others had varying degrees of warp to them. The point being is here you have examples of cues with which no particular care was taken to season the wood - all sitting in the same environment - for 16 years and some were dead straight and others were not.
I certainly believe, and my own primitive R&D confirms this, that a cue case can slow down the change in temperature and allow the cue to acclimate a slower pace. I also know that cases act as a moisture barrier, not letting more in and preventing what's inside from escaping quickly. This is dependent on the position of the case and the where the heat source is.
But I do not believe that a case protects against warping to any great degree. To a small degree certainly as anything which is a barrier to a heat or cold source is going to protect the cue that much more from whatever the heat source might do to it.
I do tend to think that it's not a good idea to leave cues in environments which are known to affect wood. I don't think anyone has any hard data on what the effects of keeping cues in hot trunks are. We all have the anecdotal stories of people who left their cues in the trunk and when they opened it later the cues were warped and the inlays popped.
To me that is just an example of the heat making the inevitable happen faster. But that's just my opinion on it. I know for a fact that I have had cues live in the trunk for months with no ill effects while others did not survive a few days.
My advice is still the same - insulate around the case if it's to be kept in the trunk and at least then you know that the temperature of the cues will change much slower and be closer to room temperature when you take the case back into a building.