They have been discussed, and some concerns have arisen. It's assumed that for party votes, the party whip is entitled to cast all of the votes available to the party. At least they know that some members are absent, so they don't need specific permission from members for every vote to cast their vote. If a member wants to cast a vote differently from rest of their party, they then do give written instruction to the whip to do that on their behalf or they might attend the chamber and do it themselves.
In other situations sometimes there have been errors with proxy votes. Particularly in some instances large parties, if they have a written proxy from another party, will cast the votes for them as well. In New Zealand we have two parties that have only one member each, and another party that has only two members. Those small parties are in coalition with the main governing party. Sometimes they'll give their proxies to the whip of that party if they are absent, and occasionally there's been an error made in the casting of those votes and, when that's been realized, usually by the small party telling the government whip, then they both come to the House and correct their vote.
It's not been tremendously problematic, and I think members have seen that it takes about a minute to cast a vote, and they can spend more time debating and less time voting. When we do have a traditional division, which we do on conscience issues maybe once or twice a year, it seems to take about 10 minutes to call the members to the House and then get them to vote. Members generally prefer this method.