Is your feature request related to a problem? Please describe.
From my understanding, at this time you can specify a minimum fleet buffer size either as a percentage (ie 20% of current capacity), or an absolute value of say 6. The issue I see with this is when the game is smaller, then a percentage value won't always make sense because it would have to be a very large percentage to have a decent number of servers in reserve.

In my case, I'm going to set a buffer size of 6. During off-hours with only having say 5-10 servers online, the percentage would have to be around 50-100% high to reach 6. That percentage would then be far too high during peak hours.

Describe the solution you'd like
My proposal would be to support having two buffer size values, and it using whichever is greater. Then I could set an absolute value of 6, and a dynamic value of 20%. Basically this would be setting a floor to the percentage value so it can not be smaller than X.

Describe alternatives you've considered
I considered some kind of service I run in the backend that would check number of instances and edit the fleet autoscaler appropriately, but this seems like it would be a useful feature to have as part of Agones.

Additional context
I would prefer to be able to use a percentage value so that it scales as the grows larger, but without a floor value for a minimum buffer size, it just won't work well for my needs.