Balance in HotA.

Naturally, obtaining these stables will require some effort, as they will have high value and will likely only generate in treasure chests.

High value - how much? If 15000 (like the scrolls of control), then on Jebus Cross they will be broken through on the first week, on others - at the start of the second week.
As a result, on the same Jebus Cross, one player will have them generate near the castle guarded by some wood, while the other will either not have them generate at all, or somewhere in the corner of the respawn. And where is the balance? Such things will simply kill the game.

"Simplification" on a surface level does not at all mean simplification on a deep gameplay level. Even with these objects, the game will become not easier, but perhaps even harder, due to greater variability in decision-making. Moreover, the main advantage of these objects is the acceleration of gameplay, which, in my opinion, is necessary for modern Heroes as an e-sport.

It should be understood that Heroes is not an e-sport and will never become an e-sport.
Game acceleration should be achieved through other means - simultaneous turns, reducing the timer, decreasing the number of restarts. This, by the way, has already been done for a long time and quite successfully. By significantly changing the gameplay, we will simply get a new game that will only cause rejection among the majority of the community.
And it won't be possible to attract a casual audience through such changes - they will just keep playing Wog against bots with insane settings.