In Advaita, as taught by Shankaracharya and handed down in the tradition, there is no strict prescription of such and such entity alone should be the saguṇa Brahman. The purpose of saguṇa Brahman is purely to enable the aspirant of the Vedāntic realization of the Nirguṇa Brahman to practice the sādhana of preparing the mind to receive that liberating knowledge. Thus, the concept of saguṇa Brahman is that which is not a natural ontological reality in Vedanta but a devised method which is used for the purpose it is intended and left behind subsequently. This ‘leaving behind’ is not any deliberate act on the part of the aspirant but a natural culmination of the attainment of the realization of the Nirguṇa Brahman as the only secondless Truth.
In the Panchadaśi of Swami Vidyāraṇya, we have, in the 9th chapter this set of verses:
पुनःपुनर्विचारोऽपि त्रिविधप्रतिबन्धतः ।
न वेत्ति तत्त्वमित्येतद्वार्तिके सम्यगीरितम् ॥ ३८॥
In spite of repeated enquiry a man does not realize the truth because
of three kinds of impediments. This has been clearly pointed out in
his Vārtika by Āchārya Sureśvara.
कुतस्तज्ज्ञानमिति चेत्तद्धि बन्धपरिक्षयात् ।
असावपि च भूतो वा भावी वा वर्तते तथा ॥ ३९॥
If you ask why the realization (which did not arise before) comes
now, we shall reply that knowledge comes only with the total removal
of impediments which may be past, present or future.
अधीतवेदवेदार्थोऽप्यत एव न मुच्यते ।
हिरण्यनिधिदृष्टान्तादिदमेव हि दर्शितम् ॥ ४०॥
Therefore even by studying the Veda and its meaning a man is not
released. This has been shown in the example of hidden gold.
अतीतेनापि महिषीस्नेहेन प्रतिबन्धतः ।
भिक्षुस्तत्त्वं न वेदेति गाथा लोके प्रगीयते ॥ ४१॥
There is the popular song saying that a monk could not realize the
truth, the impediment being his past attachment to a she-buffalo.
अनुसृत्य गुरुः स्नेहं महिष्यां तत्त्वमुक्तवान् ।
ततो यथावद्वेदैष प्रतिबन्धस्य सङ्क्षयात् ॥ ४२॥
His teacher instructed him of Brahman knowing his attachment to it (by
telling him that buffalo is the upādhi of Brahman). When the
impediment was removed, the monk realized the truth properly.
The commentator, Sri Rāmakṛṣṇa clarifies on the ‘popular saying’: A sannyāsin, in his householder life, had developed a deep attachment to a buffalo. Even after coming to be instructed of the Vedānta, he remained inattentive to the lessons. His preceptor noticed this and questioned him as to what was distracting his attention. On hearing about the disciple-monk’s buffalo-affinity, the Āchārya instructed him the highest Brahman with the buffalo-upādhi. In due course the monk became free of the past impediment, the buffalo-attachment, and realized Brahman as taught by the Āchārya and became enlightened.
Shankara has said in the Brahmasūtra bhāṣya:
स्यात्परमेश्वरस्यापि इच्छावशात् मायामयं रूपं साधकानुग्रहार्थम् ।
(Īśhwara, out of compassion, takes on, by His Maya, a form to grace
the spiritual aspirant.)
We can see from the above quotes that the buffalo-form was taken upon by Īśwara to bless that particular aspirant.
Also in the Kenopanishad Chapter 1 verse 5 (Pada Bhashya) Shankara comments as follows “तत्तस्मादन्य उपास्यो विष्णुरीश्वर इन्द्रः प्राणो वा ब्रह्म भवितुमर्हति”
Meaning: Hence the other is worshiped like Vishnu, Ishwara, Indra, or Prana can be called Brahman.
Here Ishwara means Shiva, so it is obvious that Adi Shankara places Vishnu, Shiva and even Indra at the same level at the level of Apara or Sagunabrahman.
One can add to this, the famous verse of Sureśwara in the Vārtika:
यया यया भवेत् पुंसां व्युत्पत्तिः प्रत्यगात्मनि । सा सैव प्रक्रियेह
स्यात् साध्वी सा चानवस्थिता ॥
Since the aspirants’ make-up can be varied, whichever method that
suits one is good enough. Ultimately, one has to come to the Goal.
Such means are infinite. The means do not matter at that stage.
Hence, As per Advaita there is no compulsion that Saguna brahman is restricted to only 5.