As far as I am concerned, the only times that an approach procedure can be extended outbound is if one is completing a cat A/B procedure and a cat C/D procedure lies further out and has the same height limitations, or if the MSA is at or below the platform altitude. If extending to the cat C/D procedure then that is the limit of how far one can extend.
If ATC has required or you have chosen to start the procedure at well above the published initial height then you should be able to get the height off in the required distance or ATC should offer vectors.
Making an arbitary extension could easily result in CFIT at many places.
When making a non-precision approach there is nothing wrong with being a bit high all the way round until the DA is reached provided that there is not any excessive descent rate, the approach procedures or checks are not in any way rushed and the aircraft at the DA is in a stable position to compete the approach to land. However when making the precision approach the requirement is to capture the glide from below which makes reaching the platform height a bit more critical.
If anyone can explain how an aircraft can maintain the required lateral separation from obstacles after leaving the published procedure then please let me know.
Regards,
DFC