Hi Stephanie.
You can simply go to your text frame options > Baseline options and set First base line offset to Leading.
(Keep the “Skip by leading” preference unchecked).
This should make the bottom wrapping value consistent.
However, you’ll still be facing the issue of inconsistent top gaps.
I can think of two possibilities to keep both top and bottom gap consistent.
But both require method and precision. You said that the template is made for other people to use. Meaning you’ll have to make some good training.
Option 1 : anchor your placeholder. If height if fixed, you can check “prevent manual positioning” while unchecking “prevent selection of locked objects” in General preferences. If not, you’ll have to make an object style and make sure it’s not overridden.
Of course, this option will not work if the graphic frame isn’t anchored between two paragraphs.
Option 2 : align your text on baseline grid.
Again, this will require method: graphic frame should always be aligned on the baseline grid too. Both top and bottom must be extended/reduced in order to snap to a baseline grid.
Hope that helps.
Vinny