So, according to you, tags go by object, regardless of method of use. It follows that a javelin is, always, a melee weapon.
I'm not understanding what you're getting at here. By "tags", do you mean weapon type? And if so, what does "goes by object, regardless of means of use" mean? Additionally, I showed the rule above that says that a "thrown weapon" counts as a ranged weapon when thrown. So no, there is nothing to indicate that a javelin is
always a melee weapon. It is a melee weapon with the Heavy Thrown propery, which lets it count as ranged when used in a ranged weapon attack.
Note that under that set of rules, 1 lb objects (the only weight for thrown improvised weapons), despite having an entry in a melee weapon table, cannot be used as improvised melee weapons because they are also improvised ranged weapons.
Again, what set of rules? If you mean that a ranged weapon can't be used as a melee weapon, then yeah, you're right. However, this doesn't somehow invalidate all improvised ranged weapons, nor does it mean all 1lb objects are improvised weapons. A blanket weighs at least 1lb, for example, but it wouldn't be an improvised weapon capable of inflicting damage. We're talking about things like rocks, sticks, cutlery, iron rods, chair legs, table legs, jagged pieces of metal, spikes, chains, etc... The weights listed don't mean all objects within those weight limits, just that objects used as improvised weapons must fall within those limits. You couldn't use a barrel of wine as a ranged or melee weapon, for example, since it exceeds both weight limits. You also couldn't use a table leg as an improvised ranged weapon since it's too heavy, but it would fall within the parameters for an improvised melee weapon.
Plus, one could make the argument that while you can't use a ranged weapon as a melee weapon, that you could have objects that would work as both improvised melee and improvised ranged weapons (since improvised is a different category of weapon). Rocks, for example. Not necessarily at the same time, but you could have a rock that works as an improvised melee weapon (bigger, sharper) and a rock that works as an improvised ranged weapon (smoother, smaller, easier to hold and throw). Although for the purposes of melee, I would think you would need bigger than a 1lb rock to do significant damage. The 1lb objects in that category would be more along the lines of small metal objects, like shivs or thin rods.
Further note that (extremely) hypothetical weapons (maybe there are some in the AV, I rather doubt it) with worse base state lines than the improvised weapons but with really good tags could then be used as improvised weapons while keeping the good tags.
I don't see how something can have worse than a 1d4 for damage, which is the baseline stat for improvised weapons. You would need a 1d2 (coin flip essentially), which doesn't exist in the D&D rules currently. The dagger meets the baseline stats for improvised melee and improvised ranged weapons in that it does the same damage and has the same range. However, it's not an
improvised weapon at all, but rather one designed for combat. This is why it has a proficiency bonus, whereas improvised weapons do not. It's just a low damage weapon.
Again, I don't really see what kind of point you're trying to make here. What, that they could make a weapon using a die that doesn't exist that you could use as improvised to get higher damage but still treat it as a simple or military weapon for purposes of proficiency???
Of course, for the case of melee weapons with light/heavy thrown tags, you get the more permissive case of weapons with a combined melee/thrown weapon-table entry, so you can't argue your way out of Int. Blademaster+thrown javelin by saying "an improvised weapon doesn't count as the non-improvised use and vice-versa because they are separate weapon table entries".
(btw, I was wrong on 2-handed imp. melee weapons, the weight range s 6-12)
Light/Heavy Thrown is a property of some melee weapons. This property allows them to be counted as ranged weapons when making ranged attacks. What does that have to do with being improvised? It's not an improvised weapon, it's a simple or military weapon with the Light/Heavy Thrown property. So a Javelin, for example, is a simple melee weapon with the Heavy Thrown property. This allows it to count as a ranged weapon for the purposes of throwing it as part of a ranged basic attack (or use with a ranged power). Nowhere in there is there
anything about it being an improvised weapon, or a melee weapon that has a ranged attack.
If what you're getting at here is that somehow you can have a 1lb improvised melee weapon that would also qualify as an improvised ranged weapon, then it would essentially have the thrown quality, it doesn't matter. There's no "Heavy Thrown" property for improvised weapons, which would mean that it was "Light Thrown" anyway, and would therefore key off of Dexterity, not Strength. Essentially, it would function as an improvised Dagger. This is of course assuming that there is actually a rule governing the use of improved weapons with the Light Thrown property, which there is not. If I were a DM though, I would probably allow it for a sufficiently small object...it would save us from having to track the use of two different rocks.