Would like to see Proton add the ability to customize plans a bit more.

Example:
Base Plan = Proton Unlimited
Additional Custom Email Domains = 4 added on (+3 included domains, bringing the total to 7)
Additional Proton Drive storage capacity = 1500 GB (+500 GB included storage, bringing the total storage capacity to 2 TB)
Dedicated Proton VPN Server add-on = 1 dedicated Proton VPN server
SMTP tokens = Add ability to leverage SMTP tokens

Same here. I want to take a family account, but only when I can add 6 custom domains.

Or if they add they add the function multi user support like they have now for the business plan.

Currently, Proton Family subscriptions are limited to 3 custom domains, and users who need more must upgrade to Proton Business Suite, which is significantly more expensive and includes features they may not need. Introducing an option to purchase additional domain slots separately would provide more flexibility for families and small groups without forcing an unnecessary upgrade.

I'm not a Visionary customer and only coming to Proton in March 2025 where the offerings are 3 domains for single user Unlimited, 3 for Duo and 3 for Family. Just three domains for single user Unlimited is incredibly restrictive and a block to migrating from other services. To only have three domains for Duo and Family where there are multiple people with existing domains makes these products effectively unusable.
As @Chris Barnes says, allowing many more domains on an account is probably little overhead and it may well make the suite of products much more attractive.

Numerous people have posted about how there should be more custom domains available for the six users included in a Family plan. I agree with that, but I'd even be happy if I could pay extra for more domains. I'm on Proton Business with my fiancée even though I'm not actually running a business, and you can add additional domains beyond the 10 included for a couple of dollars a month, but if I were to add our kids, who barely know how to use email yet, it would double the cost to over $500 a year for the four of us. The family plan makes WAY more sense for our use case, except that I already have almost ten domains registered to my business account just for my fiancée and I. If I could pay to add more domains to the Family plan I would switch in a heartbeat, but maybe Proton doesn't want that because I'd be paying less per year...

I have an account at fastmail and they allow up to 100 custom domains. I have 4 custom domain names with them.

I want to migrate all my emails address to Proton but I already have two other custom domain names already set up.

I have a Proton Unlimited Account.

To compete with Google Workspace you should give the higher priced plans "unlimited" domains. Workspace has a limit of 600 domains - even if you set the limit at 50 or 100 you're giving us more than the current limits of 10 or 15. This should particularly apply to Visionary customers who are currently limited to 10. I can't imagine the expense to Proton for additional custom domains is very high, the mechanisms are already built out.

Same problem here, I am not moving over my spouse and i am not upgrading for this exact reason.

I would like to see more domains for Duo and Family accounts. I have a domain for both my real and internet alias as does my spouse. This creates a total of 4. The limit of 3 domains for Duo and Family we would not be able to bring all of our existing email addresses to Proton without getting a business account or an awkward simple logon setup.

"I filed a ticket with support but was told to basically "just purchase a business plan" which is obviously something I never intend to do"

Even the business plans have limits, so it's easy to run into the same problem there.

Proton used to offer addons for services: more domains, more storage, etc. I feel like that was a good balance. The plans get probably 90% of people all the way there, and those few remaining can pay extra to expand if they want to.

I filed a ticket with support but was told to basically "just purchase a business plan" which is obviously something I never intend to do, given that I'm on a "Visionary Plan" because I believed in Proton very early on and have spent thousands of dollars on Proton services. I'm proud to be a part of the "Visionary" group and will not change to a different service tier which offers much less for higher amounts of money. That is very callous and confusing, after having such an amazing history of customer service and customer-focused experience here at Proton. I really hope you reconsider.

This is literally the top issue I have with any Proton service. Many others have similar complaints, but I believe ANY idea which expands the amount of domains is a good idea.

I'd be alright with paying extra for more custom domains above the three which come with Proton Unlimited (tho, three is a very small number for that package), but, it should be a reasonably small addon fee as it isn't much extra cost on Proton's side per custom domain.

One custom domain in Plus plan is a shame. Other providers already allow adding at least 3 custom domains. I believe Proton will make it possible in the nearest future.

Agreed. Protonmail is already expensive as hell, what should it matter how many personal domains I want to add? The domains are still for one user, so it doesn't change anything on protonmails end in terms of server load.

Totally agree!

and if you do have to purchase domains it should come with additional email addresses.

I think I will have to go visionary because of the limitations around domain and email addresses.

ProtonMail is an amazing platform and I'm really wanting to transfer my email from Gmail. One aspect that really hurts Proton is the $$$ needed for each additional custom domain. Users of GSuite can add dozens of additional custom domains to send/receive from without increasing their costs. I have 4 domains that I mainly send from, but can't stomach adding an extra $48/year just to use domains I already own. Giving users at least 5 domains standard would make a huge difference.