Can we make it clear wether a person can buy a prulink of max 5k, OR the agent can only take a full commission based on 5k? Any amount other than that, shall be regarded as investment preium I.e agent commission shall be much less.

This happens to Allianz's ILP 2 yes ago, until they lift up the 5k agent commission gap. I have seen Allianz ILP costing RM 200k per annum.

In ILP it's usually separated into 2 accounts.

1* is the protection accounts(life,36Illnesses & medical rider) which have the 5K cap . . . . well new ILP policy like the PRULINK1
    have replace the 5th & 6th series, so should not be a problem now for big sum insured
2* investment account which normally dont have any maximum cap & agent commission is only 3% from the total investment
Very simple . . . you can make an endorsement to your older policy to upgrade your medical rider
Your agent should be able to tell you the additional premium required 

The allocation part will not effect your existing policy