Title explains it well enough. Have available docks attached to space stations that can be purchased to store ships that you want to keep but don't have the fleet points available. The cost of the dock in question could be tied to the number of fleet points, increasing exponentially. For example a dock for a Wasp wing might be several 100s while a dock for a paragon might be in the 100 thousands.
The idea came from me recently acquiring a Odyssey, rendering my twin Venture class cruisers useless, I didn't want to get rid of them, as they are my 2nd and 3rd ships, but also did not want to carry them around, as they were taking up 24 valuable fleet points.