I’m not experienced with the 2018 VW TSI at all, but drawing from other realms I am familiar with...
1. Silicon sealant probably better than “hot glue” for this particular application. Hot glue melts when...hot...which the oil & oil pan typically gets.
2. What is “plastic”? Polymers have come a long way in the last decade. For example... in the firearm world (for the love of TDIs don’t make this political as what I am about to say is not at all so don’t take it there...) Magpul’s polymer magazines have outperformed aluminum & steel magazines in drop tests, crush tests, etc. The aluminum & steel mags pinch, ding, and dent while the polymer magazine does not. Subsequent function test show consistent function from the polymers mags while the aluminum & steel mags fail.
So...it depends on what type of plastic your oil pan is made out of. It may be more robust (in the short term anyway, without numerous heating/cooling cycles)
It may be a cheap brittle plastic that is easily stripped that needs an aftermarket aluminum or steel oil pan replacement and/or a panzer plate for extra protection. I don’t know. Maybe oilhammer or someone else can chime in on the quality of materials that makes up your car.
Best of luck with it however it goes. Cheers.