How is this called? Is this an Asian weapon? If so, is there a western version of this?

It's a real weapon (or at least, the movie one is based on a real weapon). There are surviving Qing Dynasty examples, but they are rare. This weapon doesn't appear in the Qing military regulations, and doesn't have an official name. The only name I've seen it called is zhanmajian, 斬馬劍, "chop horse sword", after a name used for similar Han Dynasty swords (large two-handed jian (double-edged swords), but with sword-sized handles, not polearm-sized handles). The Han swords were also called duanmajian, 斷馬劍, "cut off horse sword". The single-edged version, the zhanmadao, 斬馬刀, "chop horse knife/blade/sword" was more common.

There were double-edged long-handled executioner's swords used in China. These were usually shorter than the movie weapon (but still long), but could have handles as long as the blade. I haven't seen these called anything other than the English "executioner's sword".

Note that the Chinese dao, 刀, applies to single-edged blades of all lengths, from small knives (utility knives, kitchen knives, single-edged fighting knives), through short swords, long swords, to large polearms. Whatever the size of the blade and the size of the hilt/haft, it's a dao. Single-edged weapons like the movie weapon in question are more commonly called pudao, 樸刀, "simple/plain dao", or dadao, 大刀, "big dao" (which is also used for large single handed swords and sword-sized two-handed dao) than zhanmadao, but zhanmadao and various other names are used. If the double-edged version was more common, it's likely that a number of names would be in use.

The late Ming encyclopedia Sancai Tuhui shows a weapon with a double-edged blade and a long haft of about the same length as the blade, called the Erlang dao, 二郎刀, after the god Erlang Shen who is often depicted with a similar weapon (but often with a shorter blade and longer haft, and often with a three pointed blade; this three-pointed version an Erlang dao as well, but is also called sanjian liangren dao, 三尖兩刃刀, "three-point double-edged dao"). Usually, the non-three-point version of the Erlang dao has a fancy blade, not a simple sword blade like the movie weapon. However, the three-point weapon that accompanies the movie sword-staff weapon under discussion is the three-point Erlang dao, so the plain weapon might be intended to be the non-three-point version.

Thus, two names for the weapon: zhanmajian and Erlang dao.

I'm practicing Aikido myself and am very much into it's Jo staff-techniques for their versatility and reach, but always thought they would lack the necessary strength in a real fight, which is why I always imagined and designed a sword similar to the one in the YouTube-clip myself, with a long hilt to slide up and down on with both your hands. Would love to find out more about this, if such weapons really were a thing and what you guys think are some good/bad properties they might have.

While there are few examples of double-edged weapons like this (sword-sized blade with similar length handle), there are many single-edged examples. Weapons like this were most common in China, with various pudao/dadao/zhanmadao weapons. Most surviving examples are Qing (because recent weapons are more likely to have survived), but similar weapons were used during the Ming. Similar weapons were used in Japan: the nagamaki.

Compared to a sword with a blade of similar length, the long-handled version can allow more reach by gripping further back on the handle, gives more leverage which can be useful in close fighting (e.g., if fighting an opponent with a long polearm, and having closed in), but the long handle can restrict motion, offers a lot of space for an opponent to grab the weapon in close range, and the long-handled version is heavier. (The weight of these weapons would typically make them handle quite differently to a jo.) The full-time two-handed nature of the weapon means that no shield can be used. The length of the weapon means that it can't be worn at the belt as a wear-everywhere sidearm.

Compared to spears and long polearms, these weapons lack reach.

Thus, in many ways, these short polearms/long-handled swords combine features of both polearms and swords. This means that they also combine disadvantages of both polearms and swords, and this is probably what makes them relatively uncommon, compared to long polearms and swords.

The other weapons in the clip:

1. The weapon(s) used by the hero is the hudiedao, 蝴蝶刀, "butterfly dao" AKA baat jaam dao (Cantonese), 八斬刀, "eight chop dao".

2. The weapon introduced at 2:15 is a niuweidao, 牛尾刀, "oxtail dao".

3. At 2:50, the opponent brings out hudiedao for some hudiedao vs hudiedao.

4. The polearm at 4:00 is a ji, 戟, usually translated as "halberd", used for a variety of polearms from ancient to modern times. The same opponent draws a dao, but I can't see it clearly enough to say what specific type it is.

5. The next opponent uses a pair of lujiaodao, 鹿角刀, "deer horn knives".

6. The weapons revealed at 5:20 are improvised weapons. These are the blades from an agricultural guillotine, usually used for cutting chaff. A modern version can be seen here: https://www.chinahao.com/product/45482471847/

7. At 6:59, the opponent draws a dao that looks like a hudiedao. Hudiedao are by definition double/twin weapons, and are worn together in one scabbard. So that they fit together, the sides of the handles that sit together in the scabbard are flat (so half-oval in cross-section rather than oval). If the dao drawn here has a handle that's flattened on one side, it's one of a pair of hudiedao. Similar swords were made as single swords, with oval cross-section grips (and were typically used with shields); if this is such a sword, it would be a duandao, 短刀, "short dao".

8. The final weapon appears to be a Mauser C96 semi-automatic pistol, with shoulder-stock holster attached for use as a shoulder stock. "C96" from the year of first production, 1896 (and produced into the 1930s).

Question for OP: what is this movie? The clip was awesome and I would love to watch the entire movie.