As you told your env is already stable and no technical issue, based on your situation i would suggest
Way 1:
Don’t go with any new deloyments or changes in current prod env and it may take your production smoothly until your upgrade is ready, but it’s really tough time with out support from SAG
Way 2:
Use SAG professional service to make your easier/ you have lot option in market that can do your upgrade is very low cost.
Note: please take other advice also
#webMethods-Upgrade#webMethods-General#Integration-Server-and-ESB#webMethods