Present Subjunctive as Optative

Question

In many European languages - at least those I looked into - it is possible to use Present Subjunctive as optative mood (although often considered dated or of limited availability):

Thy Kingdom come
Dein Königreich komme
Que ton règne vienne

PIE is supposed to have had an optative and a subjunctive mood. As Latin evolved, subjunctive and optative mood merged. Proto-Germanic however, dropped subjunctive mood and optative mood became subjunctive. I wonder if Germanic languages never dropped optative mood entirely or if it was reintroduced from Romance languages/Latin at a later point; if therefore there is an unbroken ancestry between present day "subjunctive as optative mood" and PIE optative mood in Germanic languages or not.

Answer 1

If we accept the view taken by Bozzone, PIE Subjunctive was basically a Future tense. Optative mood, on the other hand, was used for wishes and hopes. Germanic Subjunctive is, at the earliest point it appears, already used for wishes and hopes (Gothic "nimai" - "may he take!") The function of Germanic subjunctive is curiously similar to French, but since both Gothic and Old Norse use the subjunctive in this way, things would seem to have been like that in Proto-Germanic, before French even existed.

So it seems like PG didn't just drop the subjuncive mood, then lacked a Subjunctive mood and later decided to use the Optative mood for that, but rather that it never had what now is its Subjunctive mood (PIE Subjunctive mood being quite unlike it) until Optative mood changed its meaning from wishes and hopes only to anything hypothetical.