What qualitative assumptions should management have in mind in pooling alternatives in making decisions and treat them as the same?

Management looks at alternatives to make decisions ...   They usually base their decisions on solid facts and numbers supported by verifiable evidene.

If assumptions are to be made, these assumptions should make sense, have some logic and rational behind them, and should be verified as soon as possible for validity.

If the assumptions cannot be validated for whatever reasons, then this should be documented, accepted and signed off by all involved parties ... just in case things turn the other way round !!

In making such decisions, there should be clear/agreed criteria for comparison and possibly for weighting and scoring among the different alternatives.  Such criteria may include cost, time, resources, complexity, risk, external dependencies, ... etc

Hopefully this answers your question,    if you need further assistance, let me know