APM Present Computername Selection during logon

APM 11.4.0 HF3

We want to do something like the following : https://devcentral.f5.com/articles/auto-launch-remote-desktop-sessions-with-apm.Upjl4hDTA34

However, instead of storing computernames in AD, we have an internal website that can retrieve a list of computers assigned to our end user (pulled from an internal DB/custom inventory repository). Some of them can have multiple PC's assigned, or none at all (would normally then prompt them for it).

After our users select a PC from this webpage, we currently utilize (legacy) MS terminal server web access to connect them but, for easier supportability and cross-platform, we want to replace this with the F5 RDP ActiveX/Java Client to ultimately get them connected to their desktop PC in the office.

I was able to sideband our custom web pc lookup form (just requires username passed via webform), retrieve the list of computers it returns. Then I'm able to split those into custom session variables with iRule's as follows:

However, how can I present this returned list to our end-users in a selection (dropdown/table etc) prior to completing the access policy? Additionally prompting our users with a text box if no such list exists? I've tried the built in decision boxes (limited to just 2 options?) but they don't seem very dynamic or customizable (Although I was able to present one of the custom variables above). Is there some other alternative that I can customize a bit more?

I am aware that the built in logon pages are accessible via advanced customization (presenting me with a ton of php/java code but was wondering if there was something a bit more accessible for me (not knowing a lot of php or java). (See a close reference of how to use this below) ... T

After they make their selection, I'd like to stuff it into : session.mycustom.cname.selected = 'mypc2' and use that as an endpoint for the Remote Desktop Resource.

Alternatively, is there was instead a way to just use our (already done) intranet web form (hosted internally)? I don't know a way to display this page during login and somehow return back to the APM Policy so I've been getting involved with doing this via iRules and behind the scenes via sideband and (probably) needing to do a bit of 'custom' logon page.

The closest example I've found is located : https://devcentral.f5.com/articles/big-ip-apmcustomized-logon-page.UpjEpxDTA34 The example above however, uses static 'data groups' where my list needs to be built dynamically from retrieved values from a webform.

If someone can point me down right path I feel it will save me a lot of time.

Thank you in advance.