I'd suggest a rhird party payment wallet—Neteller springs to mind, and theres also paypal. Google/apple pay could be another option. I can't tell you off-hand whether GG accepts the Neteller method, I've funded my deposits solely via my debit card and have never reached the ceiling amount.
Are you sure it's a regulation issue? When you sign up and create your account. you are asked to set your own limit (IIRC there was a daily ljmit and a monthly limit and you need to enter values for both of these. The cashier will not allow you to deposit more than your self-imposed limit—and these are cumulative, so my £100 daily limit means if I tried to do a sixth deposit of £20 within a 24hr period, it would fail as I'd already made five £20 deposits to reach my maximum self-imposed daily limit).
Double check the cashier page, it tells you what you set your limit at. Contact support and get it changed.
Although I do question the logic of wanting to have such a large amount of cash held outwith your bank account—your bankroll is your bankroll, regardless of where its physically (virtually?) being stored. I'd rather have my money in my bank account potentially earning me interest, instead of in GGPokers bank account earning them interest.
However I do understand the logic of seeing one sum of money in one place, of that's your intention and helps you or your mind to seperate your bankroll from other cash.
If you have that problem, of picturing it in your minds eye, then a spreadsheet might help you in this regard, and then it doesn't matter where the money is—the spreadsheet is your bankroll, and there's many very good templates downloadable, just Google them. Then the one place where you can see your total roll is the spreadsheet (or pokertracker, poker ledger, there's many apps that will help you in this regard).
Hope this helps!