1.Will the run-flat indicator light, next to handbrake stay on?
If you leave the TPMS in the Rim it will function as always
2. Will any modifications need be done to the rims?
No
3. Will this affect my carswarranty/maintance plan?
They never said anything to me
4. How would i deal in the case of a puncture, heard sumthin about a tire mobility kit?
$20 at walmart , slime and an air compressor... Get that and /or triple ato cover towing incase of a flat
5. If i have 205/45/17tyres at the moment, would 215/45/17 tires fit?
http://www.1010tires.com/tiresizecalculator.asp according to that yes ... I run 205/40/17 (More common size)
6. What make of tyre is recommended for a mini?
I've run Kuhmo , Yokohama's , Nitto's