Seriously consider a range and put it on a wall, not the island - you have better options for a vent hood if you do that. You could consider an under-cabinet MW such as the GE PEM31 which can be hung under a cabinet or mounted in an upper cabinet with a trim kit. Bosch is a good brand to consider for a mid-price range. I also would have liked a second oven in my kitchen but space precluded it - storage space was more important to me.

I would like to suggest that for big picture kitchen design issues, the gardenweb kitchen forum might be a good resource for layout questions. They tackle all kinds of thorny design issues and their insight could prove valuable.

From an appliance selection perspective, one option is consolidation. You can combine the microwave, the toaster oven, and a secondary convection oven into one box by getting a speed oven. A good speed oven will do all of the things these individual appliances can do, but better.

If costs are a concern, then going the route you're planning will be a LOT more expensive than having a range on a wall. $1200 gas cooktop and $2000 oven and the additional cabinetry needed to house the appliances (2k in a budget cabinet line, 3-5K mid) plus island ventilation (2-5K mid if you don't need makeup air engineered in your locale) really adds up fast. A simple GE Profile gas range ($2500) plus a $600 wall vent is much easier to plan around and much easier on the budget.

Thanks for the tips - I will check these out/consider the alternatives!

In our current kitchen we have a 36" Bosch Gas cook-top on one kitchen wall (galley style), below that, and to the left, a 30" Bosch convection wall oven, on the counter above a Cuisinart Stainless toaster oven, and finally, in the upper cabinets a large microwave.

We constantly use the Toaster - it is a great appliance and we cook everything from pizza, to chicken, roast veggies and of course simple things like toast.

This layout works well for our space and needs - However, in our new home we are designing we are looking for a double wall oven, an induction cook-top and still a microwave and toaster oven. We might go with one of the combo double wall oven systems that has a smaller top combination oven if we find one we like.

I don't think you would be unhappy with your ideas - it will work.

When we built our vacation home we put both the 36" gas cooktop and the 30" wall oven on the island. The gas cooktop is near the middle of the island and the under counter wall oven is in an adjacent cabinet. Since both of us cook and there are times we have adult kids helping out in the kitchen I wanted the appliances separated so that one could stir fry while someone else broiled in the oven and you wouldn't have to ask someone to move out of the way. We have a microwave on the counter of an outside wall so that's out of the way too.

This kitchen isn't as huge as the one at home but it's efficient whether you have one cook or 4 (or more). I guess it kind of mimics our home kitchen - the gas cooktop is on the island along with a prep sink while the double wall ovens are on an outside wall. So we were already in the habit of having separate but overlapping work triangles.
We've never regretted putting the wall oven under the counter.