Interesting question.
First, yes it appears to be allowed per code. Technically NFPA 24 section 1.1.2 states "This standard shall apply to combined service mains used to carry water for fire service and other uses." So I guess the code writers may have envisioned this possibility. I generally agree with you, but a quick review of the code does not come up with anything prohibiting it.
Second, will your revised installation be capable of supplying the simultaneous demands and all other applicable requirements? How long will it take before the alarms from the fire pump starting to get there attention. Do you intend to increase the jockey pump size?