You would be doing a low speed rigid rotor type balance. Depending upon the method and the type of rotor this could be trouble. For some rotor types progressive balancing has been successful; here the components are balanced and the rotor progessively stacked.
As to the balance speed, faster is not necessarly better or good with a flexible rotor undergoing a low speed balance. You do not want to get effects from the rotor flexibility.

Yes you can. This type of policy has been practiced by electric for decades on their turbine rotors which of course are flexible rotors operating speed is above first critical. In my 40 years of exposure to these low speed balancing I would estimate that about 50 percent of the time the results were acceptable or good. When we sent a turbine rotor in for partial bucket repairs the craftsmen did their work on laying out the moments with the new buckets. The service facilities that did these repairs did not have capabilities for high speed balancing, but they did have low speed balance machines and did a low speed balance . This low speed balance was within the required spec in oz/in  or gm/in. In many cases this allowed the machine to reach synchronous without issues. Depending on the low speed balance machine calibration, the skill of the operator, the balance planes available the results could vary. With my background, I did a trim balance on hundreds of these startups in The Field. Usually there are OEM's provisions for doing this . You need to make sure these provisions exist as not all the OEM's design allowed for this field balance touch up. Good Luck, JB

Thanks sir🙏

Some rotors are mostly balanced high speed, including many generators. It depends upon the rotor design.
If you have a gas turbine rotor, some manufactures get by with low speed balancing but not all do it with a low speed balance. Depends upon the rotor design, manufacturing,  and assembly.

Bill, I've seen many rotors (stream turbine) that have groves for balancing only at at their ends (first and last wheels), are this places choosed at design because of the modal characteristics expected for the rotor, or a more simple approach because it's easy to work with

If you are talking about field balancing, the end planes may be more accessable. I have seen center planes on steam and gas turbines accessable in the field (not always so easy). I think there are paractical reasons to use the end planes.
I remember trying to get the field guy to open a port for a center plane on a steam turbine. He tried for a good while but the port was frozen by rust. We made due with the end planes. This must have be a first mode problem--don't really recall the vibration data, just the trouble (Penetrating oil was used to no avail--let sit for some time, perhaps a couple of days.).

Probably I've just seen the small turbine rotors