Optimizing the frail genius?

[The Pale King]

I know there isn't a simple way around it, but I dislike the fact that constitution is an important score for everyone and so is dex to a lesser extent. I would love to make a character that is all about the power of the mind but is unhealthy, clumsy and weak. I'm thinking something like STR, DEX and CON 8 or 10 maybe 12 max, INT, WIS and CHA 16-18. Roleplay-wise someone who has always been sickly, perhaps has severe asthma or an awful immune system or even a curse that has prevented them from training physically. Is there a way to make such a character viable and interesting? What uses could a character have for all three mental stats? How can you survive having low intiative, Fort and dex saves, AC and HP?

[Lincoln Hills]

A combat-trained mount or an animal companion large enough to ride really, really helps. In addition to boosting speed, its attacks are formidable enough to discourage enemies from attempting melee. Improved Initiative is also a big help, because getting under cover or moving behind tougher allies will be central to survival.

Later on, of course, wall spells and invisiblity (or displacement) can be of great help.

[NoTongue]

Look into a class, feats or spells that offer temporary hitpoints.

If your neglecting con that that will shore up your biggest weakness.