Good question ... I've been considering purchasing a regulated PCP for a while.
To this end, I selected a Umarex Gauntlet in .177 from New England Airguns
Looks like the Altaros regulator is the only system that displays reservoir psi.
That is, without any drilling.
" This Airgun Regulator does not need drilling in the tank.
No degrade air gauge( gauge shows pressure in air tank, not regulated pressure)."
And, looks like the most simple of all to install - as well.
At least, after viewing the video it appears so.
The only drawback ... there's not U.S. distributor or dealer support for the product.