That would mean to live with a hybrid solution, more overhead and a bigger footprint. We currently deploy our JS base to web, Android and iOS (Cordova/Phonegap). It is and will remain one code base to be flexible and fast until we get "product/market fit" and until we have KPIs where we want them. This is cost effective but comes with the slowness of web-engine rendered apps. Therefore performance is big factor and we're optimizing for that.
By switching to ng2 we have have a cost-effective and performant compromise.
I don't see what is a problem to just drop in React into `<script>` tag and use for single part of the page, gradually refactoring stuff.