Signature Spell as Metamagic

Metamagic
You get 1 point per encounter  at 1st level. To signature spell a 1st level spell costs 1 point. A 2ndlevel costs 3 and a 3rd level costs 6. You get more points every odd level and can take metamagic feats to increase options.

What do you think? And don't say exprtise dice, it won't work.