What locking can I expect with DBCC CHECKIDENT(RESEED)
Its always tricky when you try to replicate Identity columns.

You should set NOT FOR REPLICATION option on the identity column when you replicate identity field column.

This way only user inserts cause the value to be incremented at the subscriber/s.

You can even assign chunks of identity values and have them self maintained at subscribers. WHen doing this, you have to be careful as 


  During a large batch insert the replication trigger is fired only once, not for each row of the insert. This can lead to a failure of the insert statement if an identity range is exhausted during an large insert, such as an INSERT INTO statement.


You can see what types of locks are generated using sys.dm_tran_locks DMV. Doing a reseed is very instantaneous and is not a big overhead. You just have to thoroughly test your idea for all possible cases to avoid any surprises.

Also, out of curiosity, how is your solution more efficient than T-Rep ? As T-Rep is tested since many many years to be more efficient than any custom/home grown solution.