It's not surprising that the Italians have methods for this hand type... I suspect that Meckwell would have, as well, if they didn't play a big club and so don't have to worry about it.
But, absent those specific agreements, I really don't see any alternative to 3
♦. It falls into the category of 'wtp?', in that it is a difficult hand, the proposed easy rebid is clearly problematic, but it is so far ahead of all other alternatives that it really is a wtp.
A fake jump shift establishes a gf.. which is almost as much an overbid as 3
♦ is an underbid. The worst problem with the fake jumpshift is that partner may fit the jumpshift suit and we may never be able to show our hand type. Partner can easily be 4=4 in the majors, and what do we bid over 3
♠, if he raises? Don't tell me that 4
♦ or 4
♥ are natural here.... they don't, not for a second, show that our jump was a fake.
And over 3
♣? 3
♣ at least has going for it that it is the most often faked jumpshift, and we can always correct clubs to diamonds at any level, unlike our problem in spades.. but we will still hate it if partner raises.
The biggest downside of 3
♦ is that partner will pass when we can make a game... but if he doesn't pass, at least we stand the maximal chance of landing in the right denomination at the right level... besides, opposite a modern 1
♥ response, we haven't made game yet
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari