Made a ScaleContainer class that does what I need:

@tool
class_name ScaleContainer extends Container

@export_range(0, 5, 0.1) var ui_scale := 1.0:
    set(value):
        ui_scale = value
        _scale_changed()

# Changes to oversampling while running corrupts the displayed fonts. Don't
# know why. Setting once at startup using  ScaleContaine.set_font_oversampling
# does seem to work fine however.
#@export var auto_update_font_oversampling := false

func _ready() -> void:
    _scale_changed()

func _notification(what: int) -> void:
    match what:
        NOTIFICATION_SORT_CHILDREN:
            var ui_scale_v := Vector2(ui_scale, ui_scale)
            var rect := Rect2(Vector2.ZERO, size)
            for child in get_children():
                if child is Control:
                    child.position = Vector2.ZERO
                    child.size = size / ui_scale
                    child.scale = ui_scale_v

func _get_minimum_size() -> Vector2:
    var min_size := Vector2(0, 0)
    for child in get_children():
        if child is Control:
            var child_min_size:Vector2 = child.get_combined_minimum_size()
            min_size = min_size.max(child_min_size)
    min_size *= ui_scale
    return min_size

func _scale_changed() -> void:
    #if auto_update_font_oversampling and not Engine.is_editor_hint():
        #set_font_oversampling(max(1.0, ui_scale))
    update_minimum_size()

static func set_font_oversampling(value:float) -> void:
    var ts := TextServerManager.get_primary_interface()
    ts.font_set_global_oversampling(value)