Is this style of fund-raising doable?

Scenario
Give investors the option to have 50% of their equity returned as cash in the event that the cash value will equal their original investment amount. The idea is to make this a LOW RISK investment for 3F's in order to gain early traction.
Example

• Investor ABC gives 10k for 10% during early round round
• Next round completes at 100k for 50%
• Investor ABC is given 10k for 5% leaving them with 5% equity

Question

If I went this route what do I need to be aware of? What are potential problems?