Outlook + iCloud/iPhone + giga mailboxes - opinions please

I have someone asking me for a fonctional setup under these conditions

• Microsoft Outlook
• Google Apps contacts/email/calendar
• 6-7 PST files for a total of ~45-50 Gb
• Syncing via iCloud to iPhone
• Windows 7/10
• No lag

Do you think a powerful setup (much RAM, SSDs) is enough? It still isn't the best method and I can't get that someone to sort their e-mail so the size shrinks to small enough to be usable on some cloud service, like gApps (too expensive to have it all there).

Right now, it's working with iCloud control panel for Windows for the sync, and the PC/Outlook is damn slow.

Looking for alteative thoughts for solutions.

Thanks