It sounds like your dehumidifiers are already programable enough by being able to set them to a desired rh with their built in humidistat. The plug in humidistats that most growers use are only needed if you have analog dehumidifiers and or humidifiers that do not have or display the rh setting.
Try to see how much you can dial things in with your current setup. You have three VPD variables to work with, if your ability to change one is limited you can focus on the other two.
How humid will your grow area get without the dehumidifier? If RH gets into the 60%'s without it and while running it can dehumidify the grow area into the high 40%'s then adjusting temps in the 70's while modifying light intensity (by height and or power) for correct leaf temps should give you all the control you need from veg to flower with what you have.
For example, in veg you could set the dehumidifier to 64% and could probably expect an actual room rh of 60-68%, keep the temps between 70-78f and as long as the leaves are staying a bit cooler than the room temps your vpd should be good.
Yes, this is how I run it now. I have AC which pulls a lot of water too, and it is a closed system with CO2.
BUT, I could do a better job of proper settings (night too which needs to be lower) if I had control over my dehumidifier like I do everything else. No doubt what I have is working, just looking to optimize.