Huawei is a massive company with a large lineup of affordable Android phones. Why can't they just fork Android just like Amazon and Microsoft? I guess they would have to come up with alternative to google play marketplace, gmaps, gmail, etc. but it's not really a big deal with the resources they have. Not to mention that the open source equivalent of these apps are serviceable.
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.