Check change management. This is a complete field that goes way over just software integration.

The principal is that every human being is active and has a voice in the future architecture (based on spec).

Architecture is easy. Getting everyone on board is not. Luckily, it seems that human being are smarter together.

If you miss that, intern conflicts, architecture rejections will bring you integration project to a big failure.

Team / product competition is way easier to manage and is may be also the way to keep a bigger market share.