Whilst I admire the OP's intentions, I would say...

If you want/need a suite, book a suite.

If you would like a suite, but it doesn't really matter then...

1. read FT threads on individual hotels. Check for reports of nice upgrades by Diamond members. Don't assume that because you stayed 30 times last year at the Hampton (or status matched from Best Western), a random Waldorf Astoria or Conrad is going to be impressed.
2. try said property. If upgraded to suite, reward hotel's generosity and return again...
3. if upgraded next stay as well, then make mental note to make that hotel your "go to" in that particular destination.

Trying to game the suite upgrade process sounds a lot like trying to blag an upgrade on a flight - it simply doesn't work 99% of the time but does fill a few newspaper inches.