There are not more than five main systems, yet combinations of these five give rise to more strategies than can ever be used. The interaction of these systems with everything else is what makes a ship, weapons are all slightly different, and most require different combinations of the five systems to unlock their true potentials.
This would take away 40% of all combination choices, because it not only limits choices on shield regeneration, but it limits the choice on shield capacity; by having no regeneration in combat, if both sides are using the same weapons and the same power regeneration, power capacity, and thrust, the one who elected to bring less shield capacity to battle will always lose. That's absolutely ridiculous, in the current meta, DPS weapons like cannons and beams lose efficiency on targets with high regeneration. Alpha weapons like missiles gain efficiency on high regeneration targets. DPS weapons gain efficiency on high capacity targets and Alpha weapons lose efficiency. Right now, you can choose to use hard counters against enemy ships if you know what they're using, and even if you're a bit smaller, you have a chance at overcoming your disadvantage.
One enemy of my faction right now is the reason why I believe the five systems to be a great idea. Before we encountered them, I thought you should always have DPS or Alpha, and while that's true to an extent, and affects your choice in power capacity vs power regeneration, it's not the whole story. We had been using DPS ships, because we were able to get a high enough capacity that Alpha weapons had trouble killing us, we thought we had found the perfect hard counter to anything that could be thrown at us. Then we found them, they had practically no shield capacity. They had practically no power regeneration. They kicked our teeth in the first time we fought. They did it by having high regeneration, and by tanking damage with their hull. Every time we shot them, we dropped their shields, and in less than a second, their shields were back up. They found our hard counter, not by using a bigger alpha gun to defeat our shields, but by using a smarter shield layout to render our weapons useless.
Shield regeneration is an important choice in ship building.