Just rip it off.

Online shopping platform got sell replacement part.
Search kdk / panasonic ceiling fan upper and lower cover.

Temporarily you can remove the lower cover while waiting for the replacement part.
Alternatively you can use duct tape to hold it up first.

And do be careful as the ceiling fan motor is very heavy.

Duct tape or just remove it and look for a replacement.

how old is your fan?

Last time my family used a KDK fan, hahahaha, its been passed down from generations to generations, from granny to my mother time. Damn their fans last really long.

not bad, 16 years.

Don't worry about safety, its all in the ceiling hook, as long that is anchored to the ceiling, is just the fan motor.

As other posters say, just purchase cover from shopee

1) Can
2) No danger assuming no one in your house tall enough to reach & touch that thing, or family member that could fly. Joke aside, also to protect wireman when wanna change your fan and not get zap by that capacitor. The capacitor zap not gonna kill ya & doesn't hurt much (when off ok), but the zap is enough to catch you off-guard, and it's dangerous cuz you on a ladder, terkejut, lost balance... jatuh..TLDR safety for the worst case scenario etc.
3) Prevent dust to those components I guess. But afaik, there are only wires + a capasitor, not something that dust would kill an appliance imo.
4) Honestly speaking,looking at the back & forth TS in this thread, I gonna assume TS is not gonna go through the trouble to disassemble the rod. Yeah it's easy for us DIYers & who have done it before. But looking at how concerned TS is with the questions, don't think TS has the confidence to do it nor wanna go to the trouble even if TS manage to figure it out.

So here is my wild idea:

[Idea 1]
1) Go back and look at your old cover. Inspect it and determine if it is made from "elastic-plastic" or "brittle plastic". A brittle one is like a plastic that breaks when you tear it with pressure, if it is elastic, you can put pressure and it will just lose shape and stretch a little.
2) If you think it is made from something that can deform but not break when applied little pressure go next,
3) Go buy the same spare part that forumers has posted before . Shop around.
4) When item arrive, inspect again and test if it can be applied pressure without breaking. If everything good go 5
5) Determine where is the screw hole.
6) We gonna make a straight cut so it can be "open" or in malay word "kangkang" the cone open a little bit. But don't make cut on the screw area. We need that screw to secure the cone back to the fan later.
7) After made the straight cut, try to kangkang the cone open just enough so it can slide through the Metal Bar of your Ceiling fan. Careful not to break it. Hence why I say this is only possible if the plastic cone is made from plastic that is somewhat elastic (even a little will do) and not hard hard brittle plastick that will break if you kangkang it.
8) After safely slide inside into position, screw it. And the straight cut that you made before, glue back or just tape.
9) Done... and then...
10) Sit down and contemplate whether or not it is worth doing the DIY at the cost of 'probably' not long-lasting solution as the structural integrity of the cone might not be 100%. Before sleep maybe you'll ask yourself "its a new cone I should have done it the proper way perhaps" 

[Idea 2]
1) Go search around a similar cone that is elastic like a cone for a lamp. Just diy and do same procedure above. Straight cut, kangkang, slide, close, tape.
2) Go shopee search "PVC Lampshade" or "tudung Lampu". You'll see those old style bulb cone cover thingy as top seach. Maybe something like this will do [it is just an idea].
3) But I would suggest you not buy online, but go physical store so that you can test test if it is elastic or hard plastic.

Juzz throwing out wild ideas only. At least with Idea 1, you can first buy the cone and then decide whether you wanna do it properly or do the DIY ones. Good luck.