There are issues with redirecting a domain to a sub-domain that are often forgotten. One is the sub-domain will, at some point, have to stand on it's own. Often, if a domain is redirected to another, the question comes up regarding deleting the original domain. Any links, trust score, site score is passed using a 301 redirect, however, if the desire comes about to delete the original domain, then these things are lost. Using a redirect is not a bad solution, it often ends up being a temporary solution and the new domain or sub-domain must stand on it's own. It becomes imperative that the new domain or sub-domain gain links, a trust score, and site score on it's own.
If the existing domain is performing well, it should be a consideration if it still makes sense to keep the domain. A decision should be made in advance. It is fine to redirect to a sub-domain, you will suffer a small loss with any 301 redirect, but it may be wise to continue to with the original domain name if it makes sense. That is a business decision regarding branding and company identity. If the company decides that a sub-domain is best, then prepare yourself to work on the sub-domains standing for the inevitable day where the company will want to delete the original domain.