another simple idea is if a hider is in a close radius of the seekers base, lock seek.
because if you thought about it, what tempts dead hiders the most to make them speckill? A quick and non-exhausting kill of a hider next to seekers spawnpoints, just switch to seek, run a few yards, kill the hider, go back to hiders team..
maybe this would make seekers know that hey blue team is locked then there is a hider in our base. unless tweak it to not show messages/sounds per team locking
another one is, is it possible to lock teams for certain players? if yes then that would be op.
for example, lock seek to all the hiders with less than 2 points. because a hider wont risk losing his points to speckill.
but the 0 point hiders on the other hand have nothing to lose.