Don't think it is that simple for a couple of reasons:

1) Without GMS, developers will need to fork their apps and reimplement everything they use Play services for today. That's non-trvial and I suspect a substantial number of developers would not be willing to do this.

2) Even if Huawei developed their own app store, IAP framework, etc, as I understand it the order in the US prevents Huawei from entering into any new business with US companies without a license. So, does that mean that FB, Twitter, et all would be prohibited from listing their apps? I believe so.