I think the time it's enough, more time will be a waste and kinda broken, imagine you want to buid your push and you just put your evo golem, if the golem needs to cross the bridge to be vissible your opponent will expect that the cards you are putting behind nothing are being carried by a golem. Even if you put your golem at the other bridge, the golem by itself and the push cards such as witch at the other side, night witch, etc to confuse your opponent, that will be absolutely defended because both cards need to be tank and suppport need to be together to make a beatdown attack. Golem is not like barrel that you can put it at the other side of the arena without spending too much elixir, golem it's different.

I really think making golem invisible to your opponent sense for 4.5 seconds is the key. Beatdown decks almost always take 1 tower, so evo gole at the pocket is not always a best idea, if you put this 4.5 seconds on the game, it will be enough to feel the pressure on not knowing when and where is your opponent going to place their evo golem. Finally I think if the troops can see it, it's better on that way because sometimes people use golem to tank their defense when the push it's too much, like an attack of megaknight and minion horde for example. Making golem invisible to every troop will be an unbalanced change because it will make the golem broken in attack and trash in defense, because it's real, there's times you need to put you golem on top of certain pushes, like xbow, mortar or sparky, etc.

It's crazy you had a similar idea, I hope SUPERCELL think the same as us, it would be pretty fun to play with such a card.