(Making sure that citizen's of Russian, Ukrainian or Polish origin will be an ardent defender's of a Latvian Latvia, while at the same time retaining pride in their identity and their ancestral culture.)

I don't understand how that could work or why it would even be desirable. From an ethnic nationalist point of view, it seems like a far better idea to support the expulsion of the foreigners rather than to integrate with them (thereby permanently changing the Latvian gene pool and identity). Certainly Russia has enough land to resettle its people.

We have much the same problem here in Dixie with millions of Northern migrants. As in Latvia, the majority of nationalists here encourage assimilation with our uninvited colonisers rather than their expulsion. It is an attitude that I do not understand because the very idea of nationalism is to guarantee the survival and advancement of the nation's blood.

However, the political changes that you seek (e.g., promoting the Latvian language, erasing communism) will probably cause many of the foreigners to self-deport.