Did Stalin view more ethnic delimitation as strengthening his own power, or what?
Not really, you have to remember Stalin's path to becoming a revolutionary was via the Georgian liberation struggles against the Russian Empire.
To quote Stalin from The Foundations of Leninism, Chapter 6 The National Question:
"For communism, on the contrary, these tendencies are but two sides of a single cause-the cause of the emancipation of the oppressed people from the yoke of imperialism; because communism knows that the union of peoples in a single world economic system is possible only in the basis of mutual confidence and voluntary agreement, and that road to the formation of a voluntary union of peoples lies through the separation of the colonies from the "integral" imperialist "whole," through the transformation of the colonies into independent states.
Hence the necessity for a stubborn, continuous and determined struggle against the dominant-nation chauvinism of the "Socialist" of the ruling nations (Britain, France, America, Italy, Japan, etc.), who do not want to fight their imperialist governments, who do not want to support the struggle of the oppressed peoples in "their" colonies for emancipation from oppression, for secession.
Without such a struggle the education of the working class of the ruling nations in the spirit of true internationalism, in the spirit of closer relations with the toiling masses of the dependent countries and colonies, in the spirit of real preparation for the proletarian revolution, is inconceivable.
The revolution would not have been victorious in Russia and Kolchak and Denikin would not have been crushed, had not the Russian proletariat enjoyed the sympathy and support of the oppressed peoples of the former Russian Empire. But to win the sympathy and support of these peoples it had first of all to break the fetters of Russian imperialism and free these people from the yoke of national oppression.
Without this it would have been impossible to consolidate Soviet power, to implant real internationalism and to create that remarkable organisation for the collaboration of peoples which is called the Union of Soviet Socialist Republics, and which is the living prototype of the future union of peoples in a single world economic system.
Hence the necessity of fighting against the national isolationism, narrowness and aloofness of the Socialist in the oppressed countries, who do not want to rise above their national parochialism and who do not understand the connection between the liberation movement in their own countries and the proletarian movement in the ruling countries.
Without such a struggle it is inconceivable that the proletariat of the oppressed nations can maintain an independent policy and its class solidarity with the proletariat of the ruling countries in the fight for the overthrow of the common enemy, in the fight for the overthrow of imperialism.
Without such a struggle, internationalism would be impossible.
Such is the way in which the toiling masses of the dominant and of the oppressed nations must be educated in the spirit of revolutionary internationalism.
Here is what Lenin says about this twofold task of communism in educating the workers in the spirit of internationalism:
"Can such education…be
concretely identical in great, oppressing nations and in small, oppressed nations, in annexing nations and in annexed nations?
"Obviously not. The way to the one goal-to complete equality, to the closest relations and the subsequent
amalgamation of all nations-obviously proceeds here by different routes in each concrete case; in the same way, let us say, as the route to a point in the middle of a given page lies towards the left from one edge and towards the right from the opposite edge. If a Social-Democrat belonging to a great, oppressing, annexing nation, while advocating the amalgamation of nations in general, were to forget even for one moment that 'his' Nicholas II, 'his' Wilhelm, George, Poincare, etc.,
also stands for amalgamation with small nations (by means of annexations)-Nicholas II being for 'amalgamation' with Galicia, Wilhelm II for 'amalgamation' with Belgium, etc.-such a Social-Democrat would be a ridiculous doctrinaire in theory and an abettor of imperialism in practice.
"The weight of emphasis in the internationalist education of the workers in the oppressing countries must necessarily consist in their advocating and upholding freedom of secession for oppressed countries. Without this there can be
no internationalism. It is our right and duty to treat every Social-Democrat of an oppressing nation who
fails to conduct such propaganda as an imperialist and a scoundrel. This is an absolute demand, even if the
chance of secession being possible and 'feasible' before the introduction of socialism be one in a thousand….
"On the other hand, a Social-Democrat belonging to a small nation must emphasise in his agitation the
second word of our general formula: 'voluntary
union' of nations. He may, without violating his duties as an internationalist, be in favour of
either the political independence of his nation or its inclusion in a neighboring state X,Y,Z, etc. But in all cases he must fight
against small-nation narrow-mindedness, isolationism and aloofness, he must fight for the recognition of the whole and the general, for the subordination of the interests of the particular to the interests of the general.
"People who have not gone thoroughly into the question think there is a 'contradiction' in Social-Democrats of oppressing nations insisting on 'freedom of
secession,' while Social-Democrats of oppressed nations insist on 'freedom of
union.' However, a little reflection will show that there is not, and cannot be, any
other road leading from the given situation to internationalism and the amalgamation of nations, any other road to this goal" (see Vol. XIX, pp. 261-62)."
So as Some Bloke said, it would undermine the whole premise of the USSR.