Expanding on TML's idea: My route idea would be the N44, Hempstead-Walt Whitman Mall via Clinton Road, Roosevelt Raceway, New Cassel, and Jericho Turnpike.
The route would follow the N35 to Roosevelt Field, then operate via Zeckendorf Boulevard, Corporate Drive, and Merchants Concourse to provide service to the Roosevelt Raceway shopping area, then follow the N35 into Westbury, where the N77 would follow the N22 to Hicksville, reverse-looping near the train station to face northbound on Newbridge Road. The N77 would then run north on Broadway to Jericho Turnpike, travel east on Jericho Turnpike into Syosset, into Crossways Park, and then on to Walt Whitman Mall.
Service would be 6 AM to 9 PM on weekdays and 8 AM to 6 PM on Saturdays, with no Sunday service (aiming for hourly service). During the rush hours, an additional bus would run Hicksville to Crossways only.
The N79 would also be adjusted so that the N79 and N44 each served Walt Whitman Mall every other hour; alternating N79s would end at Manetto Hill Road and Woodbury Road and alternating N44s would end at Crossways (Jericho and Woodland Gate on Saturdays). There would be interlining (i.e., an N79 entering Whitman Mall would leave as an N44).
Some N22s would not travel east of Roosevelt Field, but between Hicksville and Westbury, 30-minute service would be maintained. To maintain further cost neutrality, the N19 would have the number of trips that travel to Suffolk County reduced (and eliminated on Sundays).
That area along Jericho Turnpike is an untapped market that I see, as TML does too. I would have wanted to serve Syosset RR, but could not find a suitable routing that also served Crossways. Where I differ from TML, however, is that I don't feel that Old Country Road east of Roosevelt Field warrants a third bus route, but Roosevelt Raceway Mall is also underserved with only the N43 serving it, which is why I would send it via Corporate Drive and New Cassel instead of straight up Old Country Road.