Are there any issues adding mechanical implants?

Solution 1:

No, it doesn't have negative effects story-wise, however, you will temporarily lose a bit of health (which you can recover by resting). More details:

• Only the protagonist can get implants;
• Each implant has to be paid for - usually the price is around 100 shins;
• After the procedure, the protagonist will lose a couple of HP, so if you want to get a couple skills during one visit, you have to heal him up a little first. Otherwise, the protagonist may die on the surgeon's table, and nobody wants that;
• You can't learn the exact effects of a procedure until you pay for it, so here's a chart containing some useful info:

The Clawed Gauntlets: 125 Reinforces attacks without weapons by fitting the protagonist with hidden blades, which deal 4 points of physical damage points.

The Jagged Memory 110 +1 Relativistic damage to melee weapon attack.

The Encroaching Darkness 100 Replenish 8 HP. Can be used once a day.

Blood Nanites 95 Gives resistance to most negative fettles that deal damage once a turn, such as bleeding or burn.

The Numenera Analyzer 95 5% action increase in Lore: Machinery, Mystical and Natural.

The Artificial Eyeball 110 Increases perception by 1 point.

Source

Edit: However, there are indirect consequences: since you lose health after surgery, you might want to rest, which in turn moves time ahead and can affect timed events (pending execution, murder spree, the collapse of the house on the cliff).