A ship is a trade off between many factors: firepower, defence, speed, manoeuvrability, endurance, carrying capacity and cost. There’s probably more in that list as well.
To differing players in differing situations and different personal perspectives the balance point is different.
This is then further compounded by a lot of these aspects interact with each other - for example, different 50MN MWDs have different maximum speed modifiers (obvious), different capacitor usage (impacting endurance), different capacitor penalties (endurance and often overlooked - the fitting saving in a compact MWD costs you a lump of your capacitor and so reduces recharge rate), fitting requirements and costs are also a factor.
Now, I regularly fly a MWD Sacrilege with an active tank and a large battery (for “reasons”).
The best MWD outside of Faction drives on that fit is a T2. I get better capacitor stability (useful) than a compact, a better top speed than the T1 variants, the signature impact is less of an issue because it’s a HAC I take less damage with the MWD running (I’m a mixed active armour and speed tank) as I can keep traversal up.
To just say “it’s bad” because for a few use cases a lower rated module is equally good isn’t s sound basis for balance. Make the changes you suggest and my Sacrilege will be even more effective; possibly overpowered - as it is I have a choice. Do I drop to T1 modules for some aspects, or. Do I spend more on easier to fit but horribly expensive faction modules? Yeah, that T2 MWD was worth the cost of the faction battery.
The spend on the faction web was a choice.
There’s s lot more to balance than “in case X it doesn’t work therefore it’s broken” because it will work elsewhere: Assault ships, interceptors, MWD/Cloak slippery haulers. They all benefit from better prop-mods.
And as a manufacturer who’s looked at the profitability of T2 MWDs, trust me - they aren’t over priced.
And yeah: train fitting skills - that also skews the view of what works. Low skills forces more trade offs and sacrifices in a build.
It should never be possible to fully T2 fit a ship. Resource shortage drives people having to make a choice of what is less important to them. Do a lot of people “a bit of speed” is less important than damage.
For a lot of people that extra few percent speed and capacitor is rarely important - so a T2 prop-mod is rarely a priority. But as you start to understand when it is important then you’ll make the sacrifices for it.
As you may have gathered I’m content with where T2 prop-mods are. Changing them, especially as proposed will have a lot of side effects that could be problematic.
They are an option worth considering as they are. Making the a lot more cap efficient will be unbalancing in favour of speed tanking fits.
Oh, and really avoid the Compact MWDs like the plague if you’re flying a laser boat. If you can’t get a T2 on, then go for a restrained.