Apparently the statement wasn’t clear to everybody 
So let me translate - at least based on how I understand it…
(You know how with the illusion system we have stat items… and illusions, right?)
What @den said was the following:
Once their update goes out…
If the stat item is an item your character could normally use because it’s either part of the base game or you ALSO own it… then it does NOT matter what illusion it has, you will be able to use the item no matter what, and it will simply show up without the illusion in case you don’t own the illusion item.
Coincidentally though (through the use of “as long as” implying an exclusive case) that also means if the stat item is something from the BP/Bazaar that is an actual craftable and usable item - like a proper weapon (and not just a weapon skin) - that your character does not own, then you won’t be able to equip that.
This second part I feel needs more clarification… will they be able to loot such items? dismantle? do anything with?
Let me provide examples for the first part:
For example if your character only owns the base game and the Yamatai DLC
- You would be able to pick up a star metal katana that has any Bazaar / BP / etc. illusion on it and it would simply look like a standard star metal katana when you use it.
- You would be able to pick up a Yamatai katana with any illusion on it as well and it would look like a standard Yamatai katana in case you don’t own the illusion item
The following two are a bit more “shady” and subject to the “more clarification” part.
- (This is me hoping they don’t apply this change retroactively to the old DLC items in which case:) You might be able to pick up a Khitan sword illusioned as anything too
- You would potentially? NOT be able to pick up the Katana that’s currently in the Bazaar (I haven’t bought it so I don’t know if it’s a weapon or just a skin, but I’ll assume it’s a proper weapon) even if it was illusioned to look like a standard star metal katana - because you don’t own the base item.
That’s what I gathered from that statement by Dennis above 
if it’s wrong, I’m sure he’ll correct it. Would love some clarification on the “unsure” portions though