The 'Frontier' missionary is the more strategic calling as it is directly related to the Second-coming of Christ (Matthew 24:14) - we can expect a inflood of Christians called to 'Frontier' mission as the Second Coming of Christ approaches.
Expat Missionaries in 'Regular' missions should strategically be used to release an indigenous missions movement in the reached people group they minister and not focus on planting churches themselves but favilitating the locals to do so.
The main focus of a 'Frontier' missionary is to see the first indigenous church planted which they can partner with until full autonomy, moving on as the Apostolic mantle leads. This may take time as the language has to be aquired and speicalist training is needed.