It is a cool idea. Quite a few developers have in-house tools that work with their 3d applications. I've used a level layout and mission builder tool made in 3dsmax using maxscript. The only 2 drawbacks that I can see with this approach is, one, the rather high cost of some of these apps.
Quote: "XSI is so easy to customise, it just seems pointless to me, to have to program my own level creation builder ........... if I can do it all in an existing one (including the script creation/game testing)"
I take it that you would do this in XSI, and you would need to XSI to use the tool? Pretty much putting it beyond the reach of many users? Its not as expensive as some of the others, in fact as a proffesional tool it is very affordable but as a bedroom/indie developer or hobbyist, might still be a little much.
- Which is why many try to develop their own tools.
The other thing that may be an obstacle is that there may be some limitations in the application that you'r building on. I've never used XSI so I can't give an opinion. But like the tool I used in Max, it was limited. This is because, these applications cater for so many other things, and have all kinds of systems in place that it often bogs down what is needed for gamedevelopment. For example, one of the guys from DICE said they did look at developing some tools with Max, but canned the idea because it couldn't handle the amount of polygons that they wanted to throw at it, and other real time stuff. Which is why they opted to create their own, cleaner,leaner and meaner.
- Which is why many try to develop their own tools.
Building a tool as you suggest (with all the features) would be a mean task in DBP alone, but extra tools like UNITY or DarkScript may make a difference.
Another option would be to look at some other tools, like Fragmotion which has LUA scripting and is extremely affordable.
