Good, sensible plan by the club. You can find similar ticket packages or voucher systems for baseball here in the States. Very typical to see 10-game or 20-game plans offered by both major league and minor league franchises. (Note that they play 70 home games in the minors, 81 in the majors.) Minor league teams tend to be even more creative, offering Friday-Saturday-Sunday game only ticket packages or packages for only games against affiliates of particular major league teams.
The plan should pull income into the team that likely wouldn't be there if fans were only going to pay at the gate, since they've already laid out the money for the vouchers. It may also prove to be a more popular option than half-season tickets; perhaps the success/failure of this plan will help determine whether the club offers half-season tickets for the 2015/16 season.
One potential tweak to the plan would be to discount the cost-per-game (cpg) of the flexi-tickets at a lower rate than full-season tickets. That is usually the case in the baseball ticket plans here (full-season ticket cpg