Te he puesto entre ** lo nuevo a incluir

En el modelo de contents:

**
enum ModelTypeItems {
  TARIFF_CARD = 'tariffCardItem',
  IMAGE_RESPONSIVE = 'imageResponsive',
  TEXT_ITEM = 'textBlockElement',
}
**

La prop items ahora puede recibir a parte de TariffCardItem[] elementos Media[] y TextItem[]

interface TariffCardBlock {
  action?: Action
  bgColor?: string
 ** 
  items: (TariffCardItem | ImageResponsive | TextItem)[]
 **
  label?: string
  title?: string
  image?: Media
}

interface TariffCardItem {
  cardAction?: Action
  tariff: string // ID of tariff. Get rest of info from selector
  label?: string
  showBadge?: boolean
  buttons?: Button[]
  image?: Media
  **
  content?: string
  modelType: ModelTypeItems.TARIFF_CARD
  **
}

Creo que este modelo no lo tienes actualmente, habría que incluirlo:

export interface ImageResponsive {
  mediaMobile?: Media
  mediaTablet?: Media
  mediaDesktop?: Media
  alt?: string
  title?: string
  modelType: ModelTypeItems.IMAGE_RESPONSIVE
}

Nueva prop modelType

interface TextItem {
  variant?: TextVariant
  content: string
  title?: string
  subtitle?: string
  bgColor?: string
  buttons?: Button[]
  axEvents?: AxEvent[]
  boxBorder?: boolean
  boxShadow?: boolean
  highlighted?: boolean
 ** 
 modelType: ModelTypeItems.TEXT_ITEM
 **
}

En el modleo de tarifa incluir la nueva prop bgColor?: string

interface Tariff {
  id: string
  path: string
  crmId: string
  name: string
  brand: Brand
  segment: Segment
  type: TariffType
  paymentType: PaymentType
  indirectInternet: boolean
  onlyAvailableWithOwnTO?: boolean
  title: string
  cardTitle: string
  highlightedCard?: string
  priceConditions?: string
  lineAmountIncluded: boolean
  monthsOfPermanence: number
  monthsOfPromotion: number
  totalMonthlyFee: Price
  totalMonthlyFeeWithDiscounts: Price
  totalLineFee: Price
  businessDiscount?: Price
  monthlyFeeSections?: MonthlyFeeSection[]
  maxExtraLines: number
  services: Service[]
  configurationCard?: ConfigurationCard
  advantageBlock?: GenericDynamicFeatureBlock
  promotions?: Promo[]
  tariffInformation: TariffInformation[]
  stepsToJoin?: OrderStep[]
  claim?: Claim
  summaryFaqs?: GenericDynamicTextBlock
  **
  bgColor?: string
  **
}