Actually, it MAY be possible to put a Ducky TKL into a Vortex Filco case but you have to jump through a few hoops first.
You need to measure the PCB length and width, we can check it against a Filco. It needs to be the same or smaller, also nothing near the front edge can hang below the pcb or it will ground out against the case. More than one person has had stuck keys because of how tight the space is there. I cover mine with foam and electrical tape as a precaution (and sound dampening).
Obviously you need the Vortex case and you need to get a Universal plate from a group buy. To install this, you will need to de-solder every switch. Not a fun job, but there are people who can do it for you for a price if you can't.
You will then need to adapt the Universal plate to the Vortex case. You can try to fabricate something, or have me print you a set of the ones I use. Having made several sets, while they aren't that complex, I can tell you that wedging a long strip of wood in there isn't going to work.
Lastly, you may need to move some LED's and mess with the cord a bit to get it to sit inside the case.
Can it work... very likely.
Keep in mind, an aluminum case, may not be all you think it is.
They are heavy and if dropped from a short distance (especially corner first) can damage or even break your desk (mine is glass!). A Vortex equipped Filco can weigh nearly 5 pounds. It's heavy enough, that if it falls on your foot, it could break your toe. Something to consider if you move it around a lot.
Then there is static electricity, I grounded mine after I watched a spark jump nearly 5 inches from my hand to the keyboard and illuminate the LED's. No damage, but it was a surprise. Later after some work I forgot to reconnect it and again watched a 3inch spark do it again. Electronics that have a metal case, are supposed to have a grounded case, for safety, these do not. If you live in a lightening or static prone area, you might want to consider grounding it. I connected mine to the USB ground.
On the plus side, my keyboard never slides around my desk, it stays where I put it (my custom feet help). Honestly, other than that, a little noise dampening and the looks, there isn't much difference. After I got my aluminum case, I actually began appreciating plastic ones a lot more. My little Vortex Race is nice because it's so lightweight, it can be tossed onto a shelf, into a bag, etc. and not fear it breaking or damaging anything it lands on. Unlike my Filco, which could be used as a deadly weapon.