Shields as an idea are a broken concept. They fulfil the role that Frank Herbert intended in the books well enough, which is to make combat fundamentally different to modern warfare. But the explanations leave plot hole that can have any reader thinking “Wait a minute, if that’s how they work then why not…” and “But what if someone…” after giving the matter some consideration.
This is an even bigger issue with Dune as an RPG setting, because then you have to deal with the players themselves unleashing the same creativity that results on Portable Hole/Bag of Holding ranged annihilation missiles and a Decanter of Endless Water with a Ring of Shocking Grasp around the spout.
Just treat this the way that the rulebook does attempts to combine Lasguns and Shields into improvised nukes- disallow it and tell the players discussion of it isn’t permitted as part of the game’s buy-in. Doing otherwise might result in a cool game, but it will also guarantee a game that’s no longer Dune.
Now, it we’re going to talk about ways to get around shields using basic real-world tech as a thought exercise- let’s talk about flamethrowers. Or a giant garden mister that sprays concentrated acid. Or chemical warfare agents. Or the use of thermobaric munitions.
Let’s talk about why, exactly, you can’t put armour on and then use a personal shield getting the bonuses for both when any HEMA enthusiast will tell you that the rulebook’s excuse about armour slowing you down significantly isn’t even close to accurate.
Basically, Frank Herbert was a visionary who created an amazing setting but nobody is perfect and he really, really ought to have brainstormed his ideas about shield warfare with other sci-fi writers before publishing Dune.