Would expanding the Beguiling Influence invocation in this way cause any problems?

One of the warlock’s Eldritch Invocations, Beguilling Influence, bugs me. The full description is:

Beguiling Influence
You gain proficiency in the Deception and Persuasion skills.

This is fine for a warlock who doesn’t already have proficiency with those two skills, but it’s a bit weak for someone who already has one of them, and entirely useless for someone who already has both of them.

I was wondering whether it might help to get some more mileage out of this invocation if I were to change it to this:

Beguiling Influence
You gain proficiency in the Deception and Persuasion skills. If you are already proficient in either of those skills, you instead gain expertise with that skill, which means your proficiency bonus is doubled for any ability check you make with it, unless it is already benefiting from a feature, such as Expertise, that doubles your proficiency bonus.

The intention is that it wouldn’t be any different for a warlock who wasn’t already proficient, but for a character who was already quite deceptive and/or persuasive, this invocation would enhance their abilities even further.

I added the clause about it not stacking with Expertise (wording borrowed from the Prodigy feat) so that it couldn’t be exploited by a warlock/bard or some other combination.

My question is, does this seem like a good, clean change that would add to the game, or are there either balance issues that would make this problematic, either in terms of balance or going against the design of what invocations are for, or otherwise would it make far less impact than I’m expecting?