Metamagic bonus feats

[Lord Magus]

I am trying to code an ability that grant a character bonus metamagic feats. However, the list of available feats is restricted.

Starting at level 5, MM feats available are those increasing the spell level by 1; at level 10, those increasing the level by 2 are added to the list, and at level 15, those increasing the level by 3 are added.

Is there an ability somewhere that does something similar that I can base this on? (or a thread where this has been discussed in the past; I didn't find one)

The problem I see is that adding a MM feat seems to automatically adds a separate MM pick, though this pick does not seem to be bootstrapped to the feat. The level adjustment is on a field on the MM pick, not on the feat itself nor on a tag. I am having trouble trying to set a candidate expression to account for this.

[Lord Magus]

Respectfully bumping, thanks in advance for the help!