An accelerator like the one proposed here would be far faster than an 060, and that'd really give classic Amigas a well needed performance boost. 030s aren't that hard to come by, that's true, but the 060s are rare and generally go for more than most of us can afford to pay.
The 020 for the A600 and A500 is going to be awesome though, I'd gladly get a few of these once the project is finished.
I think a simple 8MB RAM card (with automatic switching to 5.5MB when the PCMCIA slot is in use) with a Real-Time Clock on it would be a nice new expansion too, and perfect for WHDLoad and basic internet stuff (even one page at a time browsing). Just like a new internal 8MB RAM/RTC/Clockport expansion for the CD32 would be awesome, especially if it had an ethernet port on it.