Before you ask:

No, you may not be a male Sailor Scout.

You however do have some other options:

Be Knight:

There are two ways to be a knights:

Have a star seed: The first is like Tuxedo Mask, they have the seed but were born male. They have much less personal power then normal senshi, but their seeds seem to have incredible potential.

Fall in Love with a Senshi: These Knights have no star seeds of their own, but have gained power in some other manner. These Warriors have, for whatever reason been drawn into service of a Senshi and fell in love with that Senshi. If the love is returned and true, the knight reincarnates when the Senshi does, and the two are inexplicietly bound together for eternety.

Be Something else:

The sailor moon Universe is full of aliens and powerfull being. You don't need to be a Senshi to have power. (Although it helps).

Try to be somewhat original here. In the Sailor Moon Universe you can be from another dimension, planet, centrury, so you have alot of wiggle room! Just don't make us wonder why no one noticed your kind running around before.