Heck, look at 1st level. You'd have a very solid defender with some quite reasonable control and a daily heal. You'll also have a perfectly good striker, very tough with some quite nice leader stuff thrown in. Even at that level you have perfectly reasonable synergies. You may not cover all the bases full-time, but for a party of 2 you can do darn well. Pick your skills carefully and consider feats and skill powers that tend to add options, you can easily make this a very effective team.
Really, when you consider the huge range of items that are available in 4e, there's not a lot you CAN'T do already. In fact I'd much sooner be a bit relaxed about what items are available at what levels in terms of getting people what they need/want for this sort of a game. As a GM give out some items that are maybe a few levels 'too high' if needed to add in some fun extra dimensions. Give away a bunch of consumables; at lower levels a lot of those are extremely effective.