About alpha ring system update risk

No,at the moment they are not allowed.

Only people in the Insider program alpha ring are testing the feature so it is something that is being released soon but at the moment anyone not in the alpha ring using custom gamerpics risks enforcement action on their account.

Custom gamerpics are only available to people in the alpha ring of the insider program at the moment.

If you are not part of the alpha ring then you can not use custom gamerpics at the moment & risk some sort of enforcement action if you do so.

If your friend is in the Xbox Insider Program, it might be that the Guide re-arrangement feature is currently in testing for the Alpha and Alpha Skip-Ahead rings. He could start the Xbox Insider App and check which ring he is enrolled in.

If he's eligible, he might have the chance to move up to an Alpha ring, but also at the risk of new stuff not working. So he should really consider if it's worth moving up to a less stable ring.

When that new feature is being released to lower rings or the general public depends on how many issues the Alpha Testers find with the feature.

Only if it's considered to run stable, it'll be released to lower rings or for general availability.

Seems you have to be invited to join the Alpha ring

https://support.xbox.com/en-US/xbox-one/console/xbox-insider-program

The current Xbox One Update Preview rings are:

• Alpha – Open on an “invite only” basis and receives updates at the earliest point in the preview window.
• Beta – Open to Xbox Insiders with a Program tenure of 3 or more months and an Xbox Insider XP Level of 5 or higher. This ring receives updates shortly after Alpha.
• Delta – Open to any Xbox Insider with a tenure of 1 or more months that has reached Xbox Insider Level 2 or higher. Depending on certain edge cases where further attention is required from Alpha or Beta rings, Delta Insiders may receive
  system updates before Beta, though this is not a common scenario. Additionally, while early system updates are not guaranteed across the Delta ring, all Delta Insiders will receive the update prior to GA.
• Omega – Open to anyone and receives system updates shortly before the GA (General Availability) release.

Change the Insider preview ring your console is enrolled in.

According to the link provided above the last update for General Availability was in July.

If your console is completely turned off and power removed, your console will miss the regular system updates for the preview, usually about 600-700 MB. If you miss a preview update and another is released the complete OS system, about 4.5 GB, will need to be downloaded to ensure the console has the latest update for that preview ring.

I'm in Alpha Skip Ahead preview and manually do at least 3 updates a week.

The other preview rings have less updates each week and the Omega ring has the least.

If you don't like the constant updates to the System OS it may be to your advantage to unenroll the console from the Insiders program.