I think wiping the skill points is a pretty reasonable thing to do.

Look at it this way, if you have a friend who is in a higher league with a Nordgen player for example and decides to build up A LOT of skill points in the bank in order to sell to a friend of his or a player in the lower leagues. Let's say he has been building up those skill points for a couple of seasons now and decides to sell it on to his lower league level friend (It will be 1* for him but to his friend it may be 5*)

Once he sells the guy on, with external communication they can tell each other that player will be the one with skill points in the bank and then the lower league guy will proceed to bid for that guy and will bid HIGHLY knowing they will get the extra skill points. Once the guy gets the player he will now be able to assign the allocated skill points on the bank and lets say that player will level up 3* greater which now gives the player an 8* superstar player which gives him dramatic advantage over the rest of the field, once this can be done with the other positions and other players he will be unstoppable.

Doing this prevents this sort of thing happening on our game, which is good. Sadly yes it does wipe out skill points but I think doing this has more advantages

I hope you do understand what I'm trying to say, because I much prefer this than the thing I mentioned above happening. You need to look at it logically to prevent people trying to beat the system.