A 68-year-old man with a 40 pack-year smoking history and chronic cough is diagnosed with COPD. Post-bronchodilator spirometry shows FEV1 45% predicted and FEV1/FVC 0.55. He has had two moderate exacerbations requiring oral steroids in the last year but no hospitalisations. According to Canadian Thoracic Society recommendations, which initial maintenance inhaler regimen is most appropriate?