Add irule via tmsh without deleting existing irules, and how to re-order

We got the same issue here, we are in the middle of upgrading all our F5's from v10 to v11.4.1 and are running into issue with our scripting. We are using EM to bring down our sites by adding a maintenance or sorry irule on the virtuals. But the EM staged changesets are based on bigpipe commands and have not find any information how to get tmsh based changeset working on EM.

In the meantime if tried the script described in: link text

In the hope it can be modified to also add irules, but it gives errors on this line:

if { [tmsh::get_field_value $vip "rules" rules] == 0 } {

Does any one has an idea what could be causing this?

Still don't understand why something as basic as adding irules is not possible in tmsh while it was in bigpipe.