"what software does the 68k Amiga need?"
From this I can only assume a 68k Amiga program otherwise I would humbly suggest a good PC cross compiling environment or a PC version of Amiga Game Maker =)
So that aside, there are plenty of Drivers that the 68k moto could benefit from - allowing for more features in sound / graphics via PCI - sadly as much as I find this area fascinating - its quite dry for most accept the the slightly unhinged / die-hard - ironically I am sure I am part of that group - I will let you work out which
Out side of that one has to consider productivity software - sadly the stock 68k moto's are not really Web-Compatible - while one could develop software on a PC to intermediate and act as an off-load engine for web-processing - this is about 68k code on x86.
while yes there is a lot of little Linux features that would be quite tasty on the Amiga - I would humbly suggest a game creating software - make a series dedicated to a specific type i.e. APGC - Amiga Platform Game Creator or APGC - Amiga Polygon Game Creator - AFGC - Amiga Fighting Game Creator.
There is a great little PC software that allows you to create ZX Spectrum games from scratch and import graphics / sound and ASM - the name escapes me at the moment - since I am only on my first coffee of the day =)
Something in between Blitz and Amos - sadly while you could boil down code related objects to a given genre - this would still require some time / dedication - possibly a small group or team - but I see some pretty heavy weight coders already post in this thread - and that is clearly something they could do, i'd like to help out with the Polygon Game Creator