I like your idea; including it with a few of my own (some are either/or options, where offering one may mean they don't need to offer others):
1. Supercharger-capable battery upgrade
2. Battery upgrade (better range, lighter weight) without cost increase
3. Battery replacement cost decrease
4. Charging inlet upgrade to Model S connector (includes firmware fix to support 80A)
5. HPCs at Supercharger stations (better if the inlet can be upgraded and HPWCs are put at Supercharging stations)
6. Nitrogen cooling system for PEM and motor, along with gearing, tire and firmware changes for vastly improved acceleration
7. Extended warranty available, just like the Model S
8. Smartphone app works with Roadster 2.0 and 2.5 (and maybe hardware upgrade for 1.5?)
9. Guaranteed continued availability of parts we need and upgrades we might want (double-din, soundproofing, adjustable suspension, etc).
10. Discounted service pack bundles, just like the Model S
I am sure there has been a thread on Roadster upgrades before; but this is useful because it's in response to a specific note and timeframe - and because some Model S features and options have given us new ideas.