In my 3 door car parcel self seem to be bit tired/broken, it barely stays on place and it has bent from other end quite badly, there has been two 6x9" speakers and I guess weight has been too much.

What kind of options there really are?

-New self - naturally best, but not very possible at the moment.
-somehow reinforcing and repairing old one?
-just ignore and lift it back to place after every bump, not very practical either.

Material seem to be quite soft, there is steel bar at bottom but from other end it seem not to be supporting anything at the moment, some kind of crack there too, maybe fiberglass job?

I built an acoustic shelf for mine its really easy using the original shelf ,

I got 3 pieces of 6mm thick mdf , 1st one cut to fit in the slot where the shelf lives second and third one a bit shorter so they could sit either side of the first one and not foul the slot where the original parcel shelf sat , glue and clamp the three pieces together .

then I laid the parcel shelf over the top and used it as a guide to cut the speaker holes ,

by bolting through the speaker cover plinth through the shelf , the new acoustic shealth and the speakers you end up with a nice , original looking acoustic shealth that because of the depth of the wood will even improve the acoustics, by only cutting the wood the depth of the slots , you can still fold the hinged part at the back allowing easy access to the boot

sorry this is the only picture I could find

Mine is cracked from where you had right side headrest's right side leg to near speaker, only visible from below but it has bended from there a lot.

Would need to straighten and fix self first to get it look even remotely good

Depending how involved you want to get Jani, I got the carpet off mine by soaking it, and the carpet then peeled off. Can then stick that onto the MDF/ply or whatever, and it still looks stock, thats how I made the speaker cabinet in Kar.

Could be that stripping carpet off is bit too much, but might do it depending a bit. There is those ugly holes in current one so might consider getting one without holes, but money says what to do now