import { Dialog } from '@microsoft/sp-dialog/lib/index';

Russell Gove, One right doesn't mean that the other is wrong. 

For dialogs you have quite a few options the option in this article by Vesa Juvonen is one way:

https://github.com/SharePoint/sp-dev-docs/blob/master/docs/spfx/extensions/get-started/building-simple-cmdset-with-dialog-api.md

Recently for one of my customer I developed a custom form solution within a TypeScript SPFx web part.

https://veenstra.me.uk/2017/06/05/office-365-sharepoint-how-to-create-forms-using-spfx/

The nice thing about the SPFx is that you can use any framework you like just add it with npm to your project and off you go. No real limitations just a lot of options. 

So far I've found it a great way to say to my customers "almost anything is possible". If it doesn't exist yet, then simply start from scratch and with simple TypeScript development you could build the forms , dialogs etc. it all depends on your requirements. 

In Vesa's article  you will find one of these options.