North & Hillard Ex. 228 includes:
Next day Caesar had again an army which, though diminished, was prepared to face all dangers manfully.
A footnote states: "Of the concessive conjunctions quamvis is most frequently used where the verb is omitted." The Answer Book gives:
Postridie igitur Caeser exercitum habuit restitutum, qui, quamvis deminutus, pericula fortiter obire paratus est.
If deploying quamvis why not use the subjunctive as the grammatical rule requires, giving quamvis deminueretur?