I do not support

Imagine the farming... Guy makes 2 alts, on both he lets them cook for 2 months. Then he deactivates active on one. Sends all of it's unallocated to the other, (up to this threshold) then sends combinative SP towards main.
If you work it as math, it's possible, but you'd effectively only gain 25% sp from this.
Main is at 13 million SP, alts have been cooked to 8mill, as you have two characters combining SP to send, their SP's could become 16 million, effectively allowing the instantaneous transaction of 3mill sp.
You could even buy boosters for your main, then omegas for your alts.

Your system would work really well, and I can't think of a way to break the rules for massive SP gain. However, I am not sure that this should be implemented.

you can start a character in 2 minutes and make 500000 sp.

no.

No, just no.

For one, it's almost pointless.
For two, it doesn't make any bloody sense.

Though I must admit, I'm shocked at the number of people who don't even care to read the entire suggestion.

I can already see a problem with the idea that you proposed even with the restrictions imposed.

The average corp in Dust will often have about 100 players. Dust University for example already has well over 1,000 players in the corp. Then there are big corps like Ancient Exiles, Molon Labe, Grupo De Asalto Chacal, etc. who obviously have way more than 100 players.

Now let's say you're a new player and you only grind up to 1 million total SP so far. You see that other players have 10 million SP on average and like to get there quick. All you have to do is join a corp with a large number of players. Let's say the corp you join has 100 players and almost all of them have close to 10 million SP anyways since many players out there nowadays have about 20-30 million SP at this point as they have been around since closed beta. It will take only 90,000 unallocated SP each to be donated to you in order to reach close to 10 million SP.

Keep in mind that 10 million SP is about the right amount of total SP needed to specialize almost completely into one profession. About 11-13 million to fully specialize.

This will mean that most new players will just gravitate to the bigger corps as the number of SP donates from each veteran player required to catch up will be inversely proportional to the number of players already in the corp.

Also, let's not forget that 100,000 unallocated SP is not that hard to recuperate nowadays. Just one week of passive SP gains will net you 171,000 unallocated SP.