Let's say a server is set up to do ECDSA signing and you want to include the requirement to provide a ECDSA signature within your Taproot tree (script path). Is this supported?
No SegWit version 1 (Taproot) doesn't support ECDSA signing at all. All signatures must be Schnorr to take advantage of the various benefits of Schnorr signatures e.g. batch verification. (Obviously SegWit version 0 still supports ECDSA and will continue to do so but SegWit version 0 doesn't support Taproot trees/MAST.) Pieter Wuille added on IRC that the only possible use case he could foresee for this would be avoiding the need to implement Schnorr signing. However, due to the changes in sighashing the signing logic needs to be changed anyway even if ECDSA was still supported.