Or simply extend the 5115g limit to Masters and be done with it.

There are more and more options coming out every month for lightweight electric airframes with composite fuses and built-up wings/stabs (a la Sickle, Nuance), all of which make weight easily with economical components. My Sickle weighs in at 10 lb 8 oz with a Himax motor and CC Phx 85HV, APC prop and Zippy batts. The older e-conversions (like Brio) are at the end of their service lives anyway, and any still out there can make 11 lb 4 oz easily. Vanquish, Monolog and (hopefully soon) the 2M Osiris are some even less expensive options.

If the goal is to keep it cheap and competitive - and not to ignite a technology race - why jack the limit up to 11 lb 14.4 oz (5.4 kg)?