"become a major issue" is a valid phrase in written English.
For example, "Global warming has become a major issue in recent years."
Downtown has become a major issue in local politics.
Waiting times for treatment will become a major issue again.
"This could become a major issue for humpback whales".
Income disparities have become a major issue in the 2012 election season.
The second is getting paid – bad debts often become a major issue.
The NSA programs have also become a major issue in the domestic politics of America's allies.
Illegal immigration has become a major issue among Republicans in the US presidential race.
Lack of health coverage has become a major issue in the presidential race.
Electric bills have become a major issue for many businesses, from hotel operators to mushroom growers.
Fish poisoning has become a major issue, due to increased temperature and acidification of sea-water.
Health care for children has become a major issue in the presidential campaign.
