Would be nice to have an official international calendar but the issue here is that the injury to a club player is increased chance of sustaining one during the international matches and would cost the league club money by paying for his salary during his time off. He could be paid by insurance but some clubs does not pay for insurance like Blue Jackets as an example.
Best time to hold an international competitions is during off-season where if there's injury during a tournament, he is more likely to come back at 100% at a training camp or close to the start of the season. Maybe the league should ask Olympics hockey tournament to be held at Summer Olympic Games rather than Winter Olympic Games. 1920 Games were held at a different date in April, rather than August and I suppose that the IIHF could do that, holding an Olympic hockey tournament months early or months after, whichever is better for hockey to hold a best of best tournament than a February dates. If there are compromises by all parties involved between NHL, IOC, IIHF, the NHL could change their regular season/ playoffs schedule to accommodate that standard international schedule. By then, the national teams would finally have their own best players to play best of best Olympic qualification tournaments.