I've been brainstorming homebrew ideas for a campaign I'm working on and this is an idea I want the most amount of feedback on. This idea's pretty weird in terms of what I've experienced playing D&D so bear with me:

What if when a creature is subject to a dexterity saving throw, they're moved to an area outside (or on the edge) of the AoE? For example, if your PC had to make a dex. save in order to avoid a fireball spell and they succeed maybe they could be pushed to the edge of the fireball's area or completely outside of it if they have Evasion. Maybe a penalty can be placed on your saving throw if there's somehow nowhere to try and dodge the fireball or a bonus placed on your saving throw if you're behind half or three-quarters cover when the fireball is cast. You could even rule that using the Shield Master feat could exempt you from this rule as the shield is the one protecting you from the effect, not your dodging skills.
This could make fights a little more dynamic as seeing a rogue or monk make a decent saving throw against a spell with some explosion effect centered directly on them while they take zero damage has always been a little strange to me.

It's likely I'm not the first person to think of this and/or this mechanic is reflected in other systems but I wanted to get a feel for how the community would react if your DM had you use this version of dex. saves.

Fireball isn't a bomb. There isn't any force being applied. The spell just creates a cloud of fire. 

I feel this makes dex saves more annoying having to think of whether this hb rule applies in that circumstance, and it also means everyone pingponging around the battlefield that will make tactics far worse, piss off melee characters, and upsets balance mechanics.

There was a feat in 3e that encoded this. You could use a reaction to reroll a dex save at the cost of falling prone. If you wanted that level of complication you could add it to 5e as a reaction. There are abilities in 5e that push creatures on a successful save.