Hello @Gaurav_Bansal,
I would like to say is that I don’t think so that some app will cross the limit of 15 - 20 mb as there are many complicated apps which are just of 5 to 10 mb
For example Pixel Wallpaper app by @iaditya_nanda
Or Tukiz Battery app by @Avijit
Which are also on PlayStore and one of my app is also on PlayStore made on 
Niotron which size only 6.2 mb
And if you want to decrease the size of your extension then re-build that Extension with Rush by @Shreyash
And Optimise that extension by using -r or -o