Hiya!
Understandable. However, with more "hard-coded" bonuses, you are opening yourself to a possibly never ending series of blatant abuses from your players. Or, almost as bad, the dreaded "ok...just
why wouldn't they have gardens, japanese water gardens, aquariums, and a room dedicated entirely to kittens? After all, they'd get a bonus of...+14!" If you're cool with that, go for it! But for me, I'd much rather have less "hard-coded" bonuses that are more subjective to the situation.
If you go with a "can't have more than a +5 bonus to Morale", then, basically, you're just giving *everyone* a +5 bonus to Morale...because, well, why only have one garden when you can have the garden, aquarium and a kitten room?
So, now you have to add in "bad Morale" to the mix. Ok, now if you have "bad airflow, muddy courtyard, little sunlight, rat infestation, etc" in order to give penalties to Morale. Now everyone feels they
need to have the garden, aquarium and kitten room just to break even.
End result? A LOT more book keeping, for absolutely no reason. Well, IMHO, of course. Some people really like adding up and subtracting all the niggling little numbers and whatnot. Maybe you are one of them, I don't know.
For me, I'm much happier with the way 5e's "core philosophy" is designed: Free-flowing, much less number crunching, a lot more DM adjudication on-the-fly.
^_^
Paul L. Ming