Sure, but if an initially-infected respiratory cell releases its "baby coronaviruses" out to the respiratory linings, away from the blood, they'll find lots mor

Sure, but if an initially-infected respiratory cell releases its "baby coronaviruses" out to the respiratory linings, away from the blood, they'll find lots more of the respiratory cell surfaces they're optimized to infect, and maybe get a ride out to other hosts on sputum. To the extent an infected cell releases its "baby coronaviruses" into the blood stream, they find a hot, chemically active environment – which is already inhospitable to their continued survival – plus a relative dearth of the respiratory cell-walls they're optimized to enter, plus a growing number of hostile antibodies. (I don't know if a coronavirus-hijacked cell can direct its fresh viruses one way or the other, but it'd probably prefer to do that if it could, and I can understand why viruses wouldn't persist long in blood compared to respiratory-membranes.) The coronaviruses are definitely active in mucosal surfaces, and carried by mucus. I haven't seen anything about, nor do I think any activity is necessarily implied, in other connective tissues.