I think you represent a very, very small subset of the population of this game. Your complaint is certainly valid, but I can't imagine this is a high priority task for Plarium :/

I always felt crit rate and speed should be added to the Great hall

there are 10 lvls to great hall for each  so in the case of crit rate it would be 1% per lvl to the max of +10% crit rate

speed would add 1 pt per lvl for a max of +10 speed at lvl 10

If you say this would unbalance the game and make  it  more pay to win. I would say to you that everyone has access to Great hall so spend  your gold medals as you see fit

Unless they want to make Platinum medals for these stats, then I am sure more work would need to be done  in plat arena to make it easier for more to access that

But I agree with OP in that something needs to be done for those who have finished Great Hall (I am not  one  of those)

The main reason to not include crit rate is because the more you add things like that, the less useful crit rate % gloves become. Even as it stands right now, they're mostly relegated to your secondary champs - getting crit rates of 60+% with substats and masteries is pretty easy right now. With GH CR%, you'd make that even easier.

They should not add speed in great hall. We knew a lot of players complaining  (they shouldn't btw) that it takes years to max great hall, speed is king, etc., adding speed in great hall will add to their frustration. 

Great hall bonuses is good as it is right now. What they should add is arena shop similar to bazaar, but uses currency gain in classic arena. 

Adding more stuff to great hall wont solve the problem. It will just postpone it. Perhaps they could add some long term medal sink. Like for example you could reroll an item for 100 gold bars.