Emon makes the best point here, nobody would ever fight unless they heavily outnumbered and outgunned the opponent.
It's bad enough that some factions are already outnumbered everywhere they go (like the order, with the ridiculous BHG and Liberty fleets against our small player base) - but now they would be completely excluded from pvp of any kind.
I dont think anyone here wants pvp to turn into 1 vs 3+ every time you log in. This also has way too much potential for increasing griefing against players.
and Dantrithor - it'd cost the average cruiser 15-20 million every time he dies to pay that 15%. So no, it's not a good idea, and I hate trading enough as-is without being forced into spending 90% of my time doing it so that I can 'afford' one pvp fight where I get ganked by a dozen bounty hunters.