If you look at the specs for the 63/28 bearing, which is dimensionally very similar to an NSR crank bearing, the max rpm when running in oil is 13,000rpm.

The NSR bearings run in oil (either injected, or premixed) and are rated to 13,500rpm or thereabouts.

As for drilling extra holes to pressure feed the bearings, there's two opinions here. One would say that the bearing will receive a good supply of oil so will (in theory) never run dry so should last longer. The second opinion is that with the pressurized oil feed the bearing will receive too much oil, which could limit it's speed of rotation.

Just a thought.

Another thought is that with premixed fuel/oil there is more than enough oil in suspension that it'll reach all corners of the cases so there's really no need to worry. In the RS125 I spannered in the Jap Championship we had one set of cases with minimum case volume (for Tsukuba), and we'd not only totally redesigned the cases and crank, but there were no oil galleries for drip feed to the mains. These were all epoxied up. The premixed fuel/oil did a good job and we never suffered failure.