As far as I remember, this is possible. 1 APP server should work fine as well. The only must-have is 2 WFEs. Steps you need to do:

1. Configure load balancing so that all traffic is redirected to another WFE if one is down;
2. Connect to one WFE, run the usual Add-SPSolution in SharePoint Management Shell;
3. Run Install-SPSolution with -Local attribute. This will deploy the .wsp locally;
4. Wait until solution is successfully deployed;
5. Restart IIS and the SharePoint Timer Job Service on that server;
6. Repeat steps 2-5 on the other WFE.

If I recall correctly, using the -Force attribute will recycle affected app pools, so be careful with that.

As far as I remember, this is possible. 1 APP server should work fine as well. The only must-have is 2 WFEs. Steps you need to do:

1. Configure load balancing so that all traffic is redirected to another WFE if one is down;
2. Connect to one WFE using RDC, run the usual Add-SPSolution in SharePoint Management Shell;
3. Run Install-SPSolution with -Local attribute. This will deploy the .wsp locally;
4. Wait until solution is successfully deployed. You can check by running the following PS command: Get-SPSolution solution.wsp | ? {$_.LastOperationDetails}. It should display True under Deployed.
5. Restart IIS and the SharePoint Timer Job Service on that server. Either manually or by running: Restart-Service sptimerv4 and iisreset;
6. Repeat steps 2-5 on the other WFE.

If I recall correctly, using the -Force attribute will recycle affected app pools, so be careful with that. I think the hardest part in all this is getting the load balancing configured properly.