I got to this line and actually said out loud, 'Yes, yes! Get him to Bath, for goodness sake!'

But I think this is JA nudging us as readers in the ribs as if to say, 'Admiral Croft has hit the nail on the head, but we know it and he doesn't - isn't this fun?'. I don't believe the Admiral would be so indelicate as to mention getting Frederick to Bath if he really had any idea of affection between him and and Anne. Whilst he is often frank in his speech, such a comment would cross a line of propriety, I believe. He speaks from innocence of that situation and a genuine desire to see his brother-in-law married.