Encumbrance armor - minor update

As I mentioned in my post about "encumbrance armor", the idea, as written, is a bit prone to abuse.

To avoid all PCs to walking around in heavy armor, 5e limits the three heaviest kinds of armor to PCs that have minimum strength of 13 or 15.

Heavy Armor
Ring Mail	30 gp	14	—	Disadvantage	40 lb.
Chain Mail	75 gp	16	Str 13	Disadvantage	55 lb.
Splint	200 gp	17	Str 15	Disadvantage	60 lb.
Plate	1,500 gp	18	Str 15	Disadvantage	65 lb.

There is no rhyme or reason to these numbers, apparently. A Str 12/13/14/15 would make a lot more sense and work perfectly well for gaming reasons.

But why not make Strength requirements for ALL kinds of armor? This is an idea I've got from Dragon Heresy. But I prefer formulas to tables. So:

The maximum number of slots you can fill with armor (including shields) is equal to half your Strength score (rounded up); otherwise, the armor reduces your speed by (at least) 10 feet.

Crisis averted!

This works quite well. For starters, to wear the equivalent of plate armor (AC 18), you'd need... Str 15!

This also bars anyone with Str less than 9 to have AC 15 armor, although light armor (and most kinds of medium armor) is still available for (almost) everybody that has proficiency in it.

You also require a bit extra Strength for using shields, which makes sense IMO, although you could always stick to the original rules and say shields have no Str requirements.

You don't have to apply this rule to monsters - maybe armor is lighter for them because of their dimensions - although it seems to work well enough as written.