That is a valid reason.
Beacon Rate = the rate at which beacons are sent.
Basic Rate = the rate at which management frames to/from the client are sent
Data Rate = the rate at which data to/from the client are sent.
As a practical matter, the power of the access points has a greater impact on roaming than changing the data and basic rates. Power affects all of the clients on the AP. You would change the data and basic rates to influence roaming of clients only on a single SSID when you don't want to affect the roaming of clients on other SSIDs. That would be the strategy.
Changing from one WLAN manufacturer to the other is tricky because it is typically from older equipment that has less receive sensitivity (ability to hear clients) to better receive sensitivity. The Aruba antenna pattern (downtilt) means that you could mount an AP with an internal antenna in the place of an external antenna.
If this is a warehouse, please see the presentation here to start: http://community.arubanetworks.com/t5/Airheads-Breakouts/Hostile-Environments-Wireless-LAN-Design-for-Warehouses/ta-p/247147
If you need more help, you should hire a professional, because warehouse deployments can be tough...