BP in arena depends only on single ninja basic stats at level 100 summed with initiative value. If you go in arena with orochimaru, iruka, gaara shippuuden for example your bp will be very very high but this doesn't mean you own the initiative.
About what praiseluka said it's true, is very easy to abuse of that system even if you need more than two accounts, i think the minimum required is 5. Anyways, since currently for servers newer than 250 is in no way possible to reach sage of six paths rank without owning hashirama or without cashing enough to catch up with the average server 100 f2p initiative players i would suggest to ban every single person that reached that goal without meeting the two conditions i said because is SURE they cheated.

The reason why you two don't get matched is because your points aren't close. Seems the game matches you only with people within a certain range from you. Lets say you have 20 points, you can be matched only with people that owns 18-22 points, regardless the rank (yes,you can be matched with a superkage -25, and not with a jonin at 25 :-P). That's why you need more than two alts to try something like that.