This is not the right move.
"ASR1001-X built-in 10 GE ports are turned on using port-based licenses. However, if the ASR1001-X is upgraded to 20G, then the two built-in ports are automatically included."
So, if you buy the FLSA1-1X-2.5-20G license you won't have to buy any port license, because a FLSA1-BIN-2X10GE-P will come together without selecting anything.
Also note that all the other port licenses and throughput upgrade licenses won't follow the same pattern. When opting to purchase them instead the above mentioned, you will have to make sure to have both the port licenses and the throughput licenses selected.
A useful link is this: